72 A. E. Verrill — Study of the family Pectinidm. 



from Entolium in not having the auricles strongly produced dorsally, 

 though their distal angles are often a little prominent. The type 

 (P. demissum) is fi-om the Jurassic formation of Germany, as is also 

 P. disciforme (brown Jura). 



Various other allied species have been described from the Jurassic. 



A considerable number of species that have been described as 

 Anmsium, from the Jurassic and Cretaceous, apparently belong to 

 this group, for they show no trace of internal lirse. Among these 

 are the following Cretaceous species: P. memhranaceum (Nils.), 

 from Europe and India ; P. illustre Stol., from India ; P. sideatellum 

 (Stol.), from India ; P. ohovatnm (Stol. as Syncyclonema), from 

 India. 



Paramusium, gen nov. Type, ATnusium JDalli Smith. 



Shell thin, rounded, much compressed ; valves nearly equal ; sculp- 

 ture nearly obsolete, diiferent on the two valves ; the lower valve 

 has concentric undulations. Auricles very small, equal. Byssal 

 notch and pectinidial teeth obsolete. The shell has a prismatic 

 structure. Internal lirae and auricular cruras well developed. 



A single pair of gills, with long, simple, separate filaments 

 (t. Dall). The foot is slender, with a byssal groove; the end is 

 much enlarged, with an oblique, expanded, concave terminal disk, 

 striated within. No labial palpi. Ocelli without pigment. The 

 structure of the animal, as described by Dr. Dall, is very different 

 from that of typical Amnsium. P. Palll ranges from 218 to 1591 

 fathoms, from the Gulf of Mexico to Barbados. Another similar 

 species, P. meridionale (Smith), was taken by the Challenger Exp., 

 off Brazil. 



Descriptions of new species and descriptive notes on others. 

 Chlamys Islandica (Chemn.) 



Ostrcea Islandica Miiller, Zool. Dan. Prod., No. 2990, 1776. Fabricius, Fauna 

 Gronl, p. 415, 1780. 



Pecten Islandicus Chemn., Conch., vii, p. 304, pi. 65, figs. 615, 616, 1784. Lamarck, 

 Anim. sans vert., ed. 2, vol. vii, p. 145. Hanley, Rec. Biv., p. 284. Gould, Invert. 

 Mass., ed. 1, p. 133, fig. 87; ed 2, p. 198, fig. 495. Verrill, Invert. Tineyard Sd., 

 etc., p. 402. G. 0. Sars, MoUusca Reg. Arcticte Norvegiae, p. 16, pi. ii, fig. 2, 1878. 



Pecten Pealei Conrad, Amer. Mar. Conch., p. 12, pi. ii, fig. 2, 1831. 



Chlamys Islandica Fischer, Man. Couch. 



Plate XVI. figs. 2-5b. Plate XX. fig. 9. Plate XXI. fig. 2. 



In this species the labial palpi (pi. xxi, fig. 3) are broad, triangular, 

 with the distal end acute, strongly flattened on the apposed surfaces. 



