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



III form this resembles /. lacera, but is easily distinguished by the 

 branched" ai)peiulages along the sides. 



Of the Lamellibranchiata some very interesting new. forms occurred. 

 The most important of these are species of Pholadomya, Mytilimeria, 

 -and Dijylodonta — thret; genera not before found on this coast. The 

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

 few described living si)ecies. The genus Mytilimeria has hitherto had 

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

 -singular species. 



Among the northern forms, not previously found south of (Jape Cod, 

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

 tenuisulcata (973) ; Nucula tenuis. 



Pholadomya arata Verrill and Smith. 



Shell triangular, short, wedge-shaped, posterior end ar.gular, 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 abroad 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 

 l)OSteriorly ; 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 

 himella, 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, aG""'"; height, 29'"'»; breadth, 26^"'". 



Stations 940, 949, 950; 09 to 330 fathoms. 



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



Mytilimeria Jiexuosa Verrill and Smith. 



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

 anterior end rather shoiter 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 vciy floxuous, owing to the broad, dee]) 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 (nXga 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 



