BALL : MOLLUSCA AND BKACHIOPODA. 405 



lated, the posterior apparently nearly smooth ; hinge line short, straight ; interior 

 smooth, a pair of small auricular crura present ; the hinge line with a minute cen- 

 tral pit and two relatively large transversely sharply striated, elongate areas rep- 

 resenting a permanent pro vinculum. Height and length, 3 ; hinge line, 2.5 ■ 

 diameter, 1.0 mm. A single valve from near the Straits of Magellan, apparently 

 tiie same species, measures 7 mm. in height. 



U. S. S. "Albatross," station 2799, in Panama Bay, in 29^ fathoms; also at 

 station 27S4, in 194 fathoms, mud, bottom temperature 51°.9 F. U. S. N. Mus. 

 110,708. 



The hinge line of this species is very much like that of P. (Pseudamusium) 

 thalassinus Dall, described in the " Blake " report. 



Pecten (Cyclopecten) cocosensis Dall, n. sp. 



Plate 6, figures 1, 3. 



Shell small, suborbicular, translucent whitish, irregularly painted with opaque 

 white, red, and ferruginous brown, in lines, zigzags, or clouded patches ; there are 

 also visible on the right valve in some of the specimens whitish rays which would 

 give the impression until the interior is examined that the shell belongs to the 

 Propeamusium group ; ears subequal, small, the anterior larger, in the left valve 

 elegantly minutely reticulated and at the hinge line adorned by a series of small, 

 close-set, short, sharp spines ; in the right valve the sculpture of the ears is verv 

 similar, but the lines are less close and sharp and the anterior auricle has a deep 

 triangular byssal sulcus, without a noticeable fasciole or a ctenolium ; left valve 

 with the umbo sharp, small, and prominent, the disk nearly smooth, with faint 

 radial striae which near the submargins become more regular and sharp, especially 

 behind ; right valve with a less prominent umbo, the surface polished, the ventral 

 margin flexible, and reflexed when closed ; sculpture of fine, close, regular concen- 

 tric lines with wider flat interspaces ; interior smooth, polished, without radial 

 lirae ; the hinge line wilh two well-marked transversely striated provincular areas. 

 Height of shell, 8.7 ; breadth, 9.0 ; hinge line, 5.0 ; diam. 2.0 mm. 



U. S. S. " Albatross," station 33G9, near Cocos Island, Gulf of Panama, in 52 

 fathoms, rocky bottom, temperature 62°.2 F. U. S. N. Mus. 122,870. 



The faint white rays on the right valve of this shell look so much like Propea- 

 musium that until T separated the valves of one of the specimens I had no doubt 

 it belonged to that group. 



AHIIJSIIJIW BOLTEN. 



PROPEAMUSIUM De Gregorio. 

 Amusium (Propeamusium) malpelonium Dall, n. ep. 



Plate 6, fleore 9. 



Shell suborbicular, of a dirty white color, very thin and frngilc, with small sub- 

 equal ears, moderately convex; beaks low, prodissoconch small, swollen, slightly 



