A. E. Verrill — Mollusca of the New England Coast. 443 



and strongly produced backward ; the posterior margin is very 

 broadly rounded, its direction nearly parallel to the opposite part of 

 the anterior margin. The edge of the shell is crenulated with a row 

 of small rounded tubercles situated just within the margin, the larg- 

 est along the ventral edge, disappearing toward the anterior end. 

 Small radial grooves run inward from between these tubercles for a 

 short distance. The ligament-area is unusually wide, somewhat con- 

 cave, with a large cartilage-pit in the middle, which is elongated in 

 a direction transverse to the ligament, with the sides parallel and the 

 apex triangular. The hinge-plate is thin in the middle, becoming 

 rather broad at each end, so that the inner margin is curved or ano-u- 

 lated in the middle. The anterior end bears about four prominent 

 rounded teeth, the outermost the largest. The posterior end has 

 four or five prominent teeth, increasing in size outwardly; the last 

 two are decidedly larger than the rest and somewhat oblique. The 

 umbos are rather prominent and the beak curves directly inward 

 towards the cartilage-pit, and is situated some distance from the 

 margin, owing to the breadth of the ligamental area. The surface is 

 covered with small, rather regular concentric undulations or ridges, 

 which are crossed by radiating lines that are not very distinct over 

 the greater part of the shell, and become nearly or quite obsolete on 

 the umbos. The epidermis is light yellowish brown, and rises into 

 series of slender hair-like processes along the radiating lines ; these 

 epidermal hairs l>ecome longer and crowded toward the margin, 

 where they are more or less united and form a marginal fringe. 



Length, 10-5™'^; height, 11'^"^; thickness, S""™ ; length of dorsal 

 margin, 5"™ ; breadth of ligament-area, 2"™. 



Station 2092, in 197 fathoms; two living specimens (No. 44,829.) 

 This species resembles L. minuta in size and general appearance, 

 but it is more obliqne and more produced ventrally, and is widely 

 different from that and all our other species, except L. plana, in hav- 

 ing a broad ligamental area and large cartilage-jjit. It is also pecu- 

 liar in the character of its hinge-margin, and in its teeth, which are 

 few in number, prominent, roiinded, and scarcely oblique, except the 

 outer ones on the posterior side. Externally the surface is smoother 

 than in most species, the radial lines being but little evident when 

 the epidermis is oiF. Although resembling L. plana in its broad 

 ligament-area, it diifers in having the ventral margin strongly crenu- 

 lated, instead of plain, and in form it is a narrower, more oblique, 

 and more swollen shell. 



