INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 463 



cies is yellowish brown in color. The lar\'a of a fly belonging to the Mus- 

 cidse, and growing to the length of three-quarters of an inch, occurs 

 beneath the sand at low-water mark, and was also dredged ofl-shore in 

 three or four fathoms of water. 



In the shallow waters and on the flats the common shrimp, Crangon 

 vulgaris^ (p. 339, Plate III, fig. 10,) is always to be found in abundance 

 where the water is not too much freshened by the rivers. The prawn, 

 PaUemonetes vulgaris^ (p. 339, Plate II, fig. 9,) is also frequent on the sandy 

 bottoms, though more abundant among the eel-grass, and this species 

 extends far up the estuaries into the mouths of rivers, where the water 

 is but little salt. 



The most abundant Annelids are^^ems virens, (Plate XI, figs. 47-50,) 

 y. Umbataj (Plate XI, fig. 51,) Bhynclioholus dibrancMatus, (Plate X, figs 

 43, 44,) B. Americanus, (Plate X, figs. 45, 46,) and Scolecolepis mridis Y., 

 (p. 345,) all of which burrow in the sand at low-water mark in the same 

 way as on the shores of the sounds. 



Under vegetable debris and stones, at high-water mark, the Halo- 

 drilhis UttoraUs (p. 324) and Clitellio irroratus (p. 324) occur in abun- 

 dance. The Liimbriculus tenuis burrows among the roots of grass at 

 high-water mark. 



The most abundant Gastropod shells are llyanassa obsoleta, (Plate 

 XXI, fig. 13,) Tritia trivittata, (Plate XXI, fig. 112,) Bittium nigrum^ 

 (Plate XXIV, fig. 154,) Astyris lunata, (Plate XXI, fig. 110,) which occur 

 on ther flats and on the bottom in shallow water, but all are more com- 

 mon among eel-grass. The Melamims bldentatus (Plate XXY, figs. 169, 

 169a) is very abundant among the grass and weeds at and just above 

 high-water mark. It contributes largely to the food of the minnows 

 and other small fishes, as well as to that of many aquatic birds. The 

 Crepidula convexa (Plate XXIII, fig. 128) is frequent on the dead shells 

 occupied by the small hermit-crab, Eupagurus longicarpus^ (p. 313,) 

 which is abundant, running over the bottom in shallow water. 



The most abundant bivalves are the long clam, Mya arenaria, (Plate 

 XXVI, fig. 179,) and 3Iacoma fusca, (Plate XXX, fig. 222.) These both 

 occur burrowing in the sand between tides, and both occur far up the 

 estuaries, where the water is very brackish, but they are most abun- 

 dant where there is a mixture of sand and mud. In the estuaries the 

 long clam is extremely abundant all along the coast from Xew Jersey 

 to the Arctic Ocean, as well as on all the northern coa sts of Europe 

 It also occurs south of Cax)e Hatteras, as at Beaufort, Xorth Carolina, 

 but in greatly diminished numbers. North of Xew York it is very ex- 

 tensively used as an article of food. North of Cape Cod it is the com- 

 mon " clam " of the fishermen ; and north of Boston it almost entirely 

 displaces, in the markets, the "round-clam,-' or " quahog," Venus mer- 

 cenaria^ which is the common clam at Xew York and farther south. 

 Along the southern coast of Xew England both species are abundant, 

 and both are sold in large quantities in the markets. South of Xew 



