136 PROCEEDINGS OP THE ACADEMY OF 



■ 



Mercenaria mortoni, Conr. 



The quahogs with prominent recurved concentric laminae are 

 common, and, so far as I am able to judge, readily distinguishable 

 from the more usual kind. Yery large specimens (five to six 

 inches) are scattered over the sand, half buried, on Bird or other 

 shoals, where I did not notice 31. violacea. I have seen boat-loads 

 brought for sale, consisting entirely of the ridged kind, and was 

 assured that they occurred in certain localities to the exclusion 

 of the other species. The fishermen seem to make a distinction, 

 and certainly I saw none that I hesitated to discriminate. Young 

 specimens (two to three inches) are quite smooth between the 

 fewer and sharper laminae ; in the largest ones the ridges become 

 blunter and more crowded, and the whole surface is rugged. 



Gemma totteni, Stm. ( Ve7ius gemma, Tott.) 

 Dredged. 



CMone cancellata, Linn. 



An abundant shell. 

 Cytherea convexa, Say. 



Strewn in numbers OA'er the beach. Of the many examples 

 gathered, all show gray or olive discoloration, and are much 

 eroded. 



"Fossil ? Stirapson does not give it, and Kurtz marks it 'N. 

 C, fossil ?' If fossil, the specimens are probably C. sayana Con- 

 rad, which he described and figured in his Miocene Fossils of the 

 United States as identical with Say's convexa ; but in his Cata- 

 logue of the Miocene Shells of the Atlantic Slope (Pr. A. N. S. 

 Phila., 1862, p. 575) he states it to be different. I have seen no 

 notice of the differences. It would be well to search for living 

 shells." 



Cytherea gigantea, Chemn. 



An abundant and conspicuous species of the sand-bars and half 

 muddy flats in the harbor ; also dredged in the channel ; not 

 seen on the beach. The colors of equally fresh specimens vary 

 much, in the general hue, and in the distinctness of the radiating 

 dark lines ; the young are generally brightest. They are al- 

 ways more or less scratched about the most convex part, where 

 much of the epidermis may be worn off. This mollusc is a 

 favorite article of food with the gulls ; the birds hold them 

 under foot much after the manner of hawks with their prej'^, and 



[July 18, 



