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 Pseudamusiwm and the more 
typical scallops. 
A few species of Amusiwm are reported from the Cretaceous, but it appears 
to be rather a modern member of the Pectiude. 
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. 8S. Fish Com. 
steamer “ Albatross” in the winter of 1884-85, at Station 2388, in 35 fms. sand, 
Lat. 29° 24’, Lon. 88° lf 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. Suits. 
Amussium Dalli Smith, Challenger Rep. Lamellibranchiata, p. 308, pl. xxii., figs. 
7 a-c, 1886. (Off Bermudas, 435 fms.) 
Amussium lucidum Jeffreys, var. striata, in part? (P. Z.S., 1879, p. 562.) 
Plate IV. Figs. la, 1b. 
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 lire (7-9) marked 
by obscure radiating ridges of the outer surface; prismatic structure in a 
radiating sense, distinctly marked, visible to the naked eye; auricles 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 fasciole, smooth or with faint growth-lines ; interior glassy, lire 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 
