MUSEUM OF COMPARATIVE ZOOLOGY. 209 



and temperate waters for the most part, and the prismatic structure of the 

 shell is especially evident in the abyssal species, which in other characters 

 differ from the type, and form a transition toward Pseudamusium and the more 

 typical scallops. 



A few species of Amusium are reported from the Cretaceous, but it appears 

 to be rather a modern member of the Pectinidce. 



A living specimen of the type species, previously only known from the 

 eastern Asiatic seas, was dredged in the Gulf of Mexico by the U. S. Fish Com. 

 steamer " Albatross" in the winter of 188-4-85, at Station 2388, in 35 fms. sand, 

 Lat. 29° 24', Lon. 88° 1' W. Gr., and dead fragments at Station 2404, in 

 60 fms., Lat. 28° 44', Lon. 85° 16' W. Gr.,both on a line between the delta of 

 the Mississippi and Cedar Keys, Florida. 



Amusium Dalli E. A. Smith. 



Amussium Dalli Smith, Challenger Rep. Lamellibranchiata, p. 308, pi. xxii., figs. 



7 a-c, 1886. (Off Bermudas, 4.35 fms.) 

 Amussium lucidum Jeffreys, var. striata, in part? (P. Z. S., 1879, p. 562.) 



Plate IV. Figs. 1 a, I b. 



Valves nearly equal, the right slightly more convex ; the adults gaping at 

 the sides ; the young closed or almost closed ; diversely sculptured ; right 

 valve nearly smooth except for growth lines, the internal lirse (7-9) marked 

 by obscure radiating ridges of the outer surface ; prismatic structure in a 

 radiating sense, distinctly marked, visible to the naked eye ; auri.;ies sculp- 

 tured only with growth lines, their upper edge denticulate in the very young, 

 arched internally, almost exactly equal, very small ; hinge line very short and 

 straight; left valve with somewhat irregular sharpish concentric waves, hardly 

 raised above the surface and more distant toward the periphery; prismatic 

 structure reticulate, the prisms almost separable at the extreme margin becom- 

 ing effaced toward the umbo with age ; auricles flat, subequal, without byssal 

 notch or fascicle, smooth or with faint growth-lines ; interior glassy, lirae 9-10, 

 usually 9, stouter longer and more opaquely white (in adults) in this valve 

 than in the other ; auricular crura very prominent, strong, forming the feet 

 of a stout arch of which the cartilage pit represents the keystone ; color trans- 

 lucent white near the margins, fuliginous in the central part which covers the 

 viscera. Alt. 62.0, lon. 59.0, max. diam. 6.0 mm., but reaching a larger size 

 as indicated by fragments. The shell is extremely thin and fragile, or rather 

 brittle. 



Obtained at Station 41 in 860 fms. in the Gulf of Mexico ; Station 117, in 

 874 fms., Lat. 17° 47', Lon. 67° 3' W. Gr. in the Caribbean Sea; Station 147, 

 off St. Kitts, in 250 fms. (bottom temperature 52°.5 F.); Station 150, between 

 St. Kitts and Nevis, in 375 fms.; Station 151, in 356 fms., off Nevis; Station 153, 

 in 303 fms., off Montserrat (bottom temperature 48°. 75); Stations 161, 162, 163, 

 and 173, off Guadalupe, in 583, 734, 769, and 734 fms.; Stations 227 and 228, 



VOL. XII. — NO. 6. 14 



