84 A. E. Verrill — Study of the family Pectinidce. 



three of the radial ribs are developed ; in such examples the vesi- 

 cles on the body ot the shell are relatively fewer, larger, and more 

 rounded and much less crowded in the radial series. In some spec- 

 imens the posterior margin below the auricle is nearly smooth or 

 marked only by the fine lines of growth, but in others, especially the 

 larger specimens, this region is covered by rather sharp granules, 

 some of which, toward the ventral margin, change to pointed scales 

 in crowded radial rows. The raised concentric lines on the right 

 valve are generally more or less appressed or sometimes imbricated ; 

 toward the ventral margin some of them show very fine microscopic 

 granulations, which are much less distinct than in P. imhrifer, as 

 figured by G. O. Sars. 



Off the eastern coast of the United States, and northward to 

 Newfoundland, in 99 to 54V fathoms. 



This species is evidently distinct from that figured by Dr. Dall 

 (Blake Mollusca, plate 4, figs. 4a, 4b), under the name of P. imhrifer. 

 His figured specimen apparently belongs to our G. siibimbrifer. 



Cyclopecten subimbrifer Verrill and Bush, sp. nov. . 



Pecten Hoshynsi Verrill, Trans. Conn. Acad., vol. v, p. 5S1, pi. xliv, fig. 11, 1882 (non 

 Forbes). 



Shell small, inequivalve, white or grayish white, translucent, length 

 and height nearly equal. Dorsal margin straight ; anterior auricle 

 in the left valve rather large and broad, the outer end obtusely 

 rounded and covered with small, close radial ribs and crowded con- 

 centric ridges ; posterior auricle much smaller, with one to three 

 faint radial ridges and many concentric raised lines ; outer end 

 forming less than a right angle, with a slight, incurved notch below. 

 In the right valve the anterior auricle has a similar radial sculpture 

 and the byssal notch is rather deep and narrow. 



The dorsal outlines of the body of the shell form rather less than 

 a right angle ; the ventral margin forms nearly a semicircle, and 

 forms obtuse angles where it meets the dorsal outlines. Umbos a 

 little prominent, with beaks small, acute, smooth, and projecting 

 beyond the margin of the hinge. The surface of the left valve is 

 covered with slightly raised concentric lines, which are raised into 

 small arched scales ; these are often semicircular, but more frequently 

 somewhat angulated or V-shaped ; they are usually separated by 

 intervals about equal to their breadth. These scales are arranged in 

 about 40 or more radial rows and decrease regularly in size to the 

 umbo, where they are replaced by thin and slightly raised radial 



