208 =A. FE. Verrill—Mollusca of the New England Coast. 
Station 1124, N. lat. 40° 01’, W. long, 68° 54’, in 640 fathoms, off 
Nantucket Island, 1882; station 2067, N. lat. 42° 15’ 25”, W. long. 
65° 48’ 40”, in 122 fathoms, 1883. 
Trachydermon exaratus (G. 0. Sars). 
Lophyrus exaratus G. O. Sars, Moll. Reg. Arct. Norvegize, p. 113, pl. 8, figs. 1, a-f, 
pl, U, fig. 1 (dentition.) 
Trachydermon exaratus Verrill, Amer. Journ. Sci., vol. xxiv, p. 365, Nov., 1882. 
PLATE XXX, FIGURES, 2, 2a, 20. 
Elongated, oblong-elliptical, strongly convex; valves distinctly 
obtusely carinated medially. Anterior valve nearly semi-circular in 
front; the posterior edge forming an obtuse reéntrant angle, with a 
rounded notch in the middle; surface distinctly radially grooved 
with single rows of rounded granules between the grooves, becoming 
larger toward the margin. 
Median valves are moderately wide, nearly straight posteriorly, 
the hinder ones with a slight median beak with distinct diagonal 
furrows and ridges, dividing them into median and lateral areas; the 
median areas are covered, on the sides, with fine but very distinct 
longitudinal grooves, with the intervening ridges narrow and 
rounded, more or less confluent and broken up into granules, near the 
diagonal lines, toward the median ridge becoming finer and irreg- 
ular, and finely granulous anteriorly and along the carina. The 
lateral areas are more elevated and covered with stronger radiating 
ridges, broken up into oblong and rounded, flattened granules, and 
separated by narrow radial furrows. The lateral insertion-plates of 
the median valves project but little beyond the upper lamina; they 
are subtruncate, with a thin notch or slit corresponding to the diag- 
onal line above. The posterior valve is transversely elliptical, with 
the posterior edge evenly rounded; the front area as in the preced- 
ing ones; the posterior area is covered with fine radial and 
concentric grooves, dividing it into radiating rows of small rounded 
granules; the articulating plates of its front edge are rather wide, 
broadly rounded or subtruncate, and separated by a broad, rounded 
median sinus; posteriorly the inner surface is marked by about six- 
teen radiating lines, terminating in thin notches of the inserted edge, 
which is very narrow and simple. 
The marginal membrane is rather narrow and covered with 
rather stout, prominent, oblong and obtuse spinules, regularly 
arranged in quincunx, their ends looking like granules ; at the edge 
and on the lower side these are replaced by small, slender spinules. 
