830 i'ffocEEHfycfi OF THE NATIONAL MUSEUM. VOL.XX. 



JEQTJIPECTEN Fischer, 1887. 



.I'.i/iii/ii'i-li'ii (suligemis of C hlamtjn) VKRRILL, Trans. Conn. Acad., X, pp. 59,67,89, 

 91. pi. xvi, figs. 6-11 ; pi. xx, figs. 1-3, 6, 6a, 1897. 



Type. JIVquipecten opercula rix ( Linn;i j us). 



Shell broadly rounded, with the valves nearly equal and symmetrical. 

 Auricles well-formed, angular; byssal notch well-developed. The sculp- 

 ture consists of a moderate number of large and nearly equal primary 

 radial ribs, which increase in size, but are not much increased in num- 

 ber with age, by the interpolation of new ones. Internal ribs or 

 flutings correspond to external grooves, but each one is bicarinate or 

 double, especially near the margins. Hinge-plate with one or two 

 slightly divergent ribs at each end, often crossed by strong transverse 

 incisions. Pectinidial teeth abortive in the type, but present in most 

 species. The foot of the type species is subcylindrical, well-developed, 

 with a byssal fissure and a terminal, deeply bilobed u scooped-shaped " 

 disk, which can be expanded. In JE. irradians l the foot has a similar 

 structure, but the terminal disk appears to be smaller. 



PECTINELLA Verrill, 1897. 

 Pet-lhifUn VERRILL, Trans. Conn. A<-ad.. X. pp. 6S. !<). !)2, 1897. 



Type. J'ectiitelhi sit/xhci (Dall). 



Shell small, thin, swollen, nearly smooth, with convex and slightly 

 unequal valves. Auricles very unequal, oblique, the anterior larger, 

 with a deep byssal notch in the right valve, but without pectinidial 

 teeth ; posterior auricle small. The surface is smooth except for fine 

 lines of growth. Camptonectes sculpture is not present. The texture 

 is not hyaline. 



The only known species is I'ectinella sigsbei (Dall) 2 which was taken 

 by the Blake Expedition in the West Indies, in 158 fathoms. 



LISSOPECTEN Verrill, 1897. 



l.ixm>l>t'<-tcn ("Mil>-riius of Chlaiityx) VEKRILL, Trans. Conn. Acad.. X, pp. (is, 90, 91, 

 1897. 



Ti/pe. Lissopecten hyalinus (Poli). 



Shell slightly inequivalve, broadly rounded, not oblique, thin, trans- 

 lucent, nearly smooth. The external sculpture consists of faint, nearly 

 obsolete radial ridges and obscure riblets, but one or both auricles may 

 have a more or less cancellated sculpture. The interior sculpture con- 

 sists of very distinct, simple, raised ribs. Auricles angular, well-devel- 

 oped. Byssal notch deep. Pectinidial teeth prominent. Margin not 

 scalloped, nearly plain and simple. 





1 Trans. Conn. Acad., X, pi. xx, lii;-. ti. 



2 Bull. Mus. Conip. Zool., XII, p. 223, pi. iv, tig. 2, 1886. 





