Sign reads: Day Use Only Except for Digging Clams Violators Vehicles Towed Away at Owners Expense and Will Be Subject to a $125.00 Fine
Sign posted at a beach on Whidbey Island, Washington. How do they determine if the vehicles belong to clam diggers? @dantheclamman.blog #MolluskMonday #MolluscMonday
A stout, brown-spotted white globular, grooved gastropod shell. English adjective order is weird. Label: "Nerita versicolor Recent Crescent Beach, St. John's County, Florida"
A stout, brown-spotted white globular, grooved gastropod shell, interior view. English adjective order is weird. The neat thing here is the aperture: it has teeth! Label: "Nerita versicolor Recent Crescent Beach, St. John's County, Florida"
I keep missing #MolluskMonday and it's time to fix that. I haven't done nerites yet, so ... here's Nerita.
🧪⚒️🐚🐌
Nerites are an old clade of gastropods, branching from more familiar taxa in the early Paleozoic. Both marine and freshwater forms survive today, colonizing land at least three times.
A large gray concretion broken in half and revealing five partial cockle shells that are white to light brown in color. It's sitting on a beach.
#molluskmonday Some spectacular Clinocardium shells in a ~40-50 lb concretion on the beach in Santa Cruz. These are earliest Pliocene (~5 myo) and from the Purisima Formation; each is about 6-8 cm in diameter.
New (old) invasive snail management technique
#MolluscMonday #MolluskMonday #JoyOfMolluscs
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A heteromorphic ammonite with a spiral conch. Blurry label: "Turrillites sp. Cretaceous Denton County, Texas"
A heteromorphic ammonite with a spiral conch. Label: "Turrillites sp. Cretaceous Denton County, Texas"
I missed #MolluskMonday, so I'm going to lead off #FossilFriday with a heteromorphic ammonite. ⚒️🧪
I always enjoyed using anomalous mollusks for fossil quizzes, just to make sure students were paying attention to the definitive qualities of each clade.
A fossil abalone in a bit of rock. The shell is a pale color in dark brown rock; the shell has ripple-like ridges and is quite flat. It's not very large, under 10 cm wide.
#molluskmonday A rare fossil Abalone (Haliotis sp.) - ornamented, but small (<10 cm). This one is from #socal and is from the upper Miocene (7-10 myo); it pre-dates the ca. 5 mya parallel evolution of giant body size in abalones - an event that likely indicates when kelp forests became widespread.
Three similar snail shells are lined up and photo'ed in black and white to show the light grid texture on the surface of their steeply pointed cone shapes
There are four very simple line drawings of what could be mouths of small animals with arrows pointing at parts of each labeled basocones
two snail shells are drawn in simple lines and stippling to show their roughly textured swirled cones and curved lip openings, with the one on the right being shorter and braider while the left has a more elongated cone
Museum Resource 🐚 #MolluskMonday
Who doesn't love a dichotomous key? The aquatic snail fauna of the southeastern United States has long been recognized for its richness and diversity. Check out our 👇
Freshwater Snails of Florida ID Guide:
www.floridamuseum.ufl.edu/iz/resources...
A mossy chiton clings to a rocky intertidal reef on the California coast. The image shows part of the chiton, “peeking” into the image. Thus, only five of the eight plates along its dorsal side are visible. The girdle surrounding the plates is covered by numerous setae - coarse bristles that give the chiton its “mossy” appearance.
Mossy *Mopalia* for #MolluskMonday! #MarineLife #MolluscMonday 🌊🦑
Five jingle shells woth varying degrees of edge damage and discoloration. Label: "Anomia Recent Crescent Beach, St. John's Co., Florida"
Shellabrating #MolluskMonday with one of my favorite encrusting bivalve taxa, Anomia. Better known as jingle shells, they do have a distinctive sound rattling in the specimen box. 🧪⚒️🦪
Reposting for #MolluskMonday, and for the relevant feeds
🦑🧪🌊🌿🌍
An unidentified bivalve mold in fine grained sandstone.
Celebrating #MolluskMonday with one of the old taphonomy lab specimens. They really broke the mold with this one! ⚒️🧪🦪
Moldic preservation involves diagenetic alteration of a fossil - in this case, a bivalve mollusk. Acidic groundwater dissolved the shell, but the exterior impressions survived.
Adding to #MolluskMonday and limpet discourse with ... wait a second. That's a keyhole limpet, Fissurella. They're not true limpets (Patellogastropods)!
🧪🐚
Ah, yes, convergent evolution strikes again.
Only this time, it remembered to add an exhaust pipe!
Grumpy cuttlefish
A totally normal rock and certainly not a cuttlefish
It's #MolluskMonday everybody! Today, it's irritable cuttlefish. 🦑
I feel you, cuttles.
Chambered nautilus phragmocone, dorsal perspective. The outer wall is damaged, revealing hemispherical inner septa separating camerae, each with a small, calcified nozzle indicating the location of the siphuncle.
Chambered nautilus phragmocones in side view. The outer wall of the one on the left is damaged, revealing hemispherical inner septa separating camerae, although the siphuncle cannot be seen from this perspective. The living chamber is damaged but visible, revealing a pearly, nacreous luster. The one on the right is a fragmented partial phragmocone, damaged after an apparent attempt to cut a sagittal section. The logarithmic progression of hemispherical septa is clearly visible.
#MolluskMonday represents today with Nautilus, a modern chambered cephalopod. Like ammonites, nautiloids have an external conch and lived in the final chamber, using the camerae for floatation. However, ammonites were much more closely related to coleoids like Spirula, with its intenal conch. ⚒️🧪
A pair of clam shells, slightly askew, protruding from a gray sandstone concretion. There is a circular drill hole from a predatory snail in the clam.
#molluskmonday A well-preserved clam (Macoma sp.) with a naticid snail boring, protruding from a fine sandstone concretion. Middle Pleistocene Port Orford Formation, Oregon.
A collection drawer full of disarticulated unionid freshwater mussel shells. Some are fragmented, others whole. Two index cards identify these as JKQM (Jack Kovach Quaternary Mollusk) Collections 53 & 54. Collection 53 comes from the north shore of the Senecaville Reservoir (Guernsey Co.), while 54 is from the southern shore (Noble Co.). Both collected March 1969.
#MolluskMonday means moar mollusks, so here's a small selection of a large collection of unionid bivalves (a diverse clade of freshwater mussels) collected by my predecessor, Jack Kovach, in 1969. I estimated around 1500 specimens in Jack's drawers (wait) when they got transferred to Cincinnati. ⚒️🧪🦪
#MolluskMonday is also 2/2 World Bivalve Day, so ... let's make a hash of it! 🧪⚒️🦪
Shell hash, specifically.
This is an oyster shell bed in the making, central Oregon coast.
Close up of a carbonate beach composed mostly of oyster shells and fragments.
Not all beaches are quartz sand ... this one is predominantly calcite, in the form of a heavily reworked oyster shell gravel. #MolluskMonday 🦪
Carbonate workers can fight over what to call this once lithified: a skeletal grainstone (Dunham), biosparite (Folk) or rudstone (Embry & Klovan).
Two shells of the bivalve Panopea, the geoduck. Siphonal gap to the right, interior view above, external below.
In under the wire for #MolluskMonday with the geoduck, Panopea.
🦪⚒️🧪
These are deep burrowing, long-lived bivalves with obscenely long siphons used for suspension feeding and respiration from a meter or more under the sediment surface. The gape and pallial sinus hint at the large, fleshy siphon.
Snails 🐌 from the German periodical ‘Das Buch der Welt,’ 1860.
#naturalhistory #snailart #MolluskMonday #animalart
Also appropriate for #MolluskMonday!
Nautiloid fossil, a tightly coiled (involute) logarithmic spiral with straight septa. Label: "Eutrephoceras deyaki Pierre Shale - Cretaceous Wasta, South Dakota "
It's the first #MolluskMonday of 2026! Sticking with the Cretaceous, we have a nautiloid from the Pierre shale of South Dakota. This was deposited in deep waters of the Cretaceous Interior Seaway, which divided North America into Appalachia and Laramidia. ⚒️🧪
A tiny brown snail on stucco with my fingertips dwarfing it. It is only 3-4 mm long, shell is disc shaped and held laterally. Visible growth lines in the shell
For #molluskmonday, Discus rotundatus. Native to Europe but broadly introduced in N. America. Sounds like they're not as destructive as garden snails and mind their own business in leaf litter. Hadn't seen one before in North LA County where my mom lives! Small population at nearby Descanso Gardens.
Tan, strongly ridged bivalve mollusk fossil. Label: "Trigonia ventricosa Sunday's River Formation, Cretaceous South Africa"
It's the last #MolluskMonday of 2025, not to mention #InverteFest! Trigoniids barely survived the end-Cretaceous mass extinction, but Neotrigonia is hanging on still ... for now.
Small, high-spired gastropod crawling up the glass inside an aquarium. Everything is VERY BLUE because of the UV blacklight.
#MolluskMonday 🐚🧪 sometimes means hanging out and catching some rays.
No, wait. I mean "rays" here like UV in a blacklight tank designed to show off reef fluorescence.
I don't think this snail could snag a whole ray.
OTOH, @laurasita.bsky.social has a story about an apple snail and fish ...
Long, tapering conical shells of orthocone nautiloids, with well defined septa.
#MolluskMonday ... Here we have densely packed phragmocones of late Ordovician orthocone nautiloids, a highlight of the Cincinnatian limestones. 🧪⚒️
One of my favorite field trip outcrops was a slab of nautiloid shells oriented parallel to wave ripples in the spillway at Caesar Creek.
Scallop and epibionts, including barnacles and bryozoans.
#MolluskMonday, #Crustmas edition: scallop encrusted with acorn barnacles! Bonus cheilostome bryozoans, but don't miss the abraded barnacle base plates either. 🧪⚒️🦪
Smooth, green columella? ✅ Open umbilicus? ✅ Bright red-orange foot? ✅ I was so excited to find a Norris’ topsnail (*Norissia norrisii*) hiding under the rockweed canopy the other day! 😍🐌 #MolluscMonday #MolluskMonday #MarineLife #Invertebrate 🦑🌊
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