THE NAUTILUS. 47 



NOTES ON SOME CAPE COO MOLLUSCA. 



BY C. W. JOHNSON. 



During a recent trip on Cape Cod, Mass., I was mostly interested 

 in studying the insect fauna, but incidentally collected a number of 

 shells. One ofternoon, at low tide I wandered over the sand-flats of 

 Provincetown harbor ; on my way out I met a little Portuguese boy 

 (Portugese, by the way, constitute about one-third of the population) 

 with a bucket full of periwinkles {Litorina litorea). I asked him what 

 he was going to do with them. " Eat 'em," was his reply. To my 

 inquiry whether they were good, he said, " Yep." The piling and 

 rocks (the remains of an old pier) were literally covered with them ; 

 over almost everything was a coating of small barnacles {JSalanus 

 balanoides), and it was interesting to see the load carried by some of 

 the periwinkles, often greater in size than the shell itself. 



On every hand were trails of the sea-snails, but I was suprised to 

 find that Polinices (^Neverita) duplicata far outnumbered P. {Lunatid) 

 heros ; the former were much smaller than those I have collected on 

 the New Jersey coast, and their nidimental bands, popularly known 

 as " sand collars," were also correspondingly smaller. The nidus of 

 P. duplicata is readily distinguished from those of P. heros by the 

 lower or expanded margin being undulated or wavy. One specimen 

 of Columbella avara was found. Of the Pelecypods, Pandora gould- 

 ana was abundant, and two specimens of the old Cytherea convexa 

 Say (which we must now call Callocardia morrhuana Linsley), were 

 collected. In places the coarse sand had a dark purple line. Close 

 inspection showed it to be made up of the little Gemma gemma. 



At Eastham are located a number of large fresh-water ponds, 

 with no apparent inlet or outlet, in which the water is very clear, 

 and quite cool. In the one nearest the station, called Depot Pond, 

 I found three species of the Unionidce. All of them were undersized, 

 and very much eroded, features characteristic of still water, even 

 though apparently more pure than many streams. The specimens of 

 Unio complanatus were about two inches in length. It was by far the 

 most common species, although dwarfed Lampsilis radialus, about 

 two and a quarter inches in lejigth, with a thick, dark , sparsely rayed 

 epidermis, was also abundant. The other species was a very fragile 

 example of Anodonta cataracta Say (^A.Jluviatilis Dillw.), about two 



