GO 8 EEPORT OF COMMISSIONER OF FISH AXD FISHERIES. 



in the anciont Tiulian slioU-honps on tlio coast of ]\rassaclnis('tts, on the 

 islands in Caseo ]^>ay, and at Dainariscotta. Thesliolls, in a soiiii-f'ossil 

 state, have been dng* np iiom deei)» beneath the nuid in the harbor of 

 Porthind, JMaine, in larfje qnantities, bnt native oysters appear to bo 

 entirely extinct in Casco Bay. Vary abnndant in Lony- Island Sound ; 

 in the upper part of Buzzard's Bay ; rare and local in Vineyard Sound ; 

 very abnndant on the shores of IMaryland and Vir,uinia. IMonth of 

 Saint John's Biver, and in Tampa Bay, Florida (Conrad). Texas 

 (Kcenier). 



Fossil in the Post-Pliocene at Point Shirley, Massachusetts, ISTan- 

 tucket Island (abundant), Gardiner's Island; in the Pliocene of South 

 Carolina; and in the Miocene of Virginia and South Carolina. 



The occurrence of large quantities of oyster-shells benealh the har- 

 bor mud at Portland, associated with Venus mercenaria, Pecteri irradianfiy 

 TurboniUa intcrrupta, and other southern species, now extinct in that 

 locality, and the occurrence of the first two species in the ancient In- 

 •lian shell-heaps, on some of the islands in Casco P>ay, though not now 

 found living among the islands, indicates that the temi)era.ture of those 

 waters was higher at a former period than at present. These facts also 

 point to the most satisfiictory explanation of the existence of numerous 

 southern shells, associated with the oyster and Venus mercenarla in the 

 southern part of the Gulf of Saint Lawrence, though not now found in 

 the intermediate waters, along the coast of Maine, nor in the Bay of 

 Fundy. 



All the various forms of this species, upon which the several nominal 

 species, united above, have been based by Lamarck and others, often 

 occur together in the same beds in Long Island Sound, and may easily 

 be connected together by all sorts of intermediate forms. Ev'en the 

 same specimen will often have the form of horcaUs in one stage of its 

 growth, and then will suddenly change to the Vlrginiana style, and, 

 perhaps, later still, will return to the form of horealis. Or these differ- 

 ent forms may be assumed in reverse order. Great variations in the 

 number and size of the costa^ and undulations of the lower valve occur, 

 both in different specimens from the same locality, and even in the 

 same specimen, at different stages of growth. All these variations 

 occur in precisely the same way in the shells taken from the ancient In- 

 dian shell-heaps along our entire coast, from Florida to Maine. 



TUN CATA. 



SACCOBRANCHIA. 



CiONA TENELLA Verrill. (p. 411).) 



American Journal Science, ser, iii, vol. i, p. 99, figs. 12, 13, 1871. AschJia fcnella 

 Stinipsoii, Proc. Bust. Soc. Nat. Hist., iv, p. '2"28, 1853 ; Inv. of Grand Matiaii, p. 

 yo, 1853; lUnney, in Gould, Invert., cd. ii, p. 24,1870. ? Afnidia occllula Ag., 

 Proc. Amer. Assoc, for Adv. Sci., ii, p. 159, 1850 (description insuflicient); Bin- 

 ney, in Gould, Invert., ed. ii, p. 24, Plate 24, fig. 332, 1870. 



Cape Cod to Gulf of Saint Lawrence; rare and local south of Cape 



