HO. 1139. in-:i-:r-]\'ATKii M <> f. /,r.vr./_; [:/; HILL AND nrsir. 835 



It is probable, however, that it grows to a much larger si/e than any 

 of the specimens obtained. 



It is named in honor of Mr. James B. Benedict, for several year^ 

 zoologist in charge on the steamer Albatross, through whose; care and 

 great interest so many small species were brought to light. 



CHLAMYS COSTELLATA Verrill and Bush. 

 (Plato LXXXVIJ lig. 6.) 



Chlamijs costellata VERRILL and BUSH, iu VERIULL, Trans. Conn. Acail., X, pp. 75, 

 91, 1897. 



Shell small, thin, translucent, bluish white, covered on both valves 

 with continuous, elevated and somewhat thickened, well-separated, 

 radiating riblets, of which there are more than thirty in the left valve 

 of the largest example. Length of the shell considerably less than its 

 height. Dorsal hinge-margin elongated, especially on the anterior end. 

 In the right valve the anterior auricle is considerably elongated, 

 obtusely rounded or subtruncated at the end, with a wide, angular 

 byssal notch beneath it, having two or three pectinidial teeth; it has 

 a broad, smooth, angular area next the body of the shell, above which 

 there are three well-marked, angular, radial ridges, separated by wider 

 concave interspaces; the posterior auricle is small, triangular, the outer 

 corner forming a little more than a right angle, and the posterior mar- 

 gin nearly straight, without any distinct notch. The dorsal margins of 

 the body of the shell are nearly straight and diverge at less than a 

 right angle; the ventral margin is pretty evenly rounded, a little 

 produced in the middle. The beak is small, acute, appressed, and does 

 not project beyond the margin. The radial ribs are very distinct, clean 

 cut, thickened, rounded at the summit, separated by nearly smooth 

 intervals, two or three times as broad as the ribs themselves; the ribs 

 increase regularly in width from near the urnbo to the margin; a few 

 intermediate ridges commence near the margin. The left valve is 

 badly broken ; it is, however, somewhat more convex than the other, 

 and the radial ribs are crossed by numerous concentric striatious giving 

 them a finely crenulated or beaded appearance; the anterior auricle is 

 broad, triangular, the outer end slightly rounded, with a slight incurved 

 notch below; it is crossed by about six small, radial ribs, similar to 

 those on the body of the shell; raised lines of growth also occur at 

 irregular intervals. Inner surface smooth and lustrous, showing the 

 grooves corresponding to the external ribs and also a very distinct 

 microscopic structure, but it is destitute of radial lira 1 . Internally, the 

 hinge margin is thin and narrow, with a sharply impressed, subinar- 

 ginal groove on each side; the resilial pit is excavated in the margin 

 of the hinge itself: the anterior auricle has internal grooves correspond- 

 ing to the external ribs. 



Length of the largest specimen, <> mm.; height, G.a mm. 



Three live specimens, at two stations, off the Grand Banks, in 07 to 

 72 fathoms, 1885-86. 



