648 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



In form this resembles I. lacera, but is easily distinguished by the 

 branched appendages along the sides. 



Of the Lamellibranchiata some very interesting new forms occurred. 

 The most important of these are species of Pholado^nya, Mytilimeria, 

 and Diplodonta — three genera not before found on this coast. The 

 PJioIadomya is more related to certain fossil forms than to any of the 

 few described living species. The genus Mytilimcria has hitherto had 

 very few living representatives, and none of them resemble our verj^ 

 singular species. 



Among the northern forms, not previously found south of Cape Cod, 

 are the following : Mya truncata ; Spisula ovalis (975, 976, 981) ; Leda 

 tenuisulcata (973) ; Nucula tenuis. 



Fholadoniya arata Verrill and Smith. 



Shell triangular, short, wedge-shaped, posterior end aisgular, some- 

 what produced, obtuse ; anterior end very short and abruptly truncated, 

 clearly defined by a carina extending from the beak to the outer margin ; 

 anterior to the carina there is a broad concave furrow, which bounds the 

 slightly convex central area of the front end ; the greater part of the sides 

 of the shell is covered with deep, rather wide, concave furrows, separated 

 by elevated, sharp-edged ribs ; the furrows vary in width and decrease 

 posteriorly ; a small portion, near the tip of the posterior end is covered 

 only by slight ribs. The surface between the ribs is finely granulated. 

 When the thin superficial layer is removed the surface is pearly. The 

 umbos are prominent, strongly incurved, nearly or quite in contact. 

 The hinge in the right valve consists of a small, slightly prominent 

 lamella, running back as a low ridge, and separated from the margin of 

 the shell anteriorly, and from the cartilage-lamina posteriorly, by a nar- 

 row groove ; the cartilage-pit is long, running forward under the beak 

 as a narrow furrow ; it is bounded internally by a prominent lamella. 

 Length, 3Q^^ ; height, 29'^'» ; breadth, 26°''". 



Stations 940, 949, 950; 69 to 330 fathoms. 



Three specimens, all dead, but one is very fresh. 



Mytilimeria flexuosa Verrill and Smith. 



Shell obliquely cordate, short, higher than long, very swollen, the 

 anterior end rather shorter than the posterior ; umbos very prominent, 

 beaks much incurved, pointed and turned forward, with a small, deep 

 concavity just under and in front of them. The outline and surface of 

 the shell is very flexuous, owing to the broad, deep grooves and ele- 

 vated ribs which divide the surface into several areas. The most promi- 

 nent rib is very high and rounded, and runs from the beak to the ex- 

 treme ventral margin, inclining somewhat forward ; in front of this the 

 anterior area is flattened with a wide, shallow, concave groove or undu- 

 lation in the middle, and others less marked ; the front edge is broadly 

 rounded, slightly undulated below. The middle area is very elevated, 

 and forms more than a third of the shell ; it is flattened or slightly 



