MUSEUM OF COMPARATIVE ZOOLOGY. 223 



Pecten (Pseudaxausitun) Sigsbeei Dall. 



Plate IV. Fig. 2. 



Valves rather convex, the left cue most so ; both apparently polished, but 

 with microscopic silky concentric stria ; no radiating sculpture, no prismatic 

 markings ; anterior auricles well marked, very small, oblique; posterior auri- 

 cles larger, with a broad shallow byssal sulcus but no fasciole or pectinium, 

 the markings only of concentric growth lines ; color brownish with opaque 

 white splashes. Alt. 11.5; Ion. 9.1 ; diam. max. 3.75 mm. 



Two \'alves were obtained by Sigsbee in 158 fms., Lat. 22° 10', W. Lon. 

 82° 20', near Havana, Cuba. This little sjjecies is very recognizable by its 

 plump oval shape, like an apricot stone, and its smooth surface destitute of 

 radiating sculpture. 



Genus HINNITES Defrancb. 

 Hinnites Adamsi, n. s. 



Plate V. Fig. 6. 



Shell thin, ashy white externally, internally semi-nacreous ; rounded with a 

 comparatively short straight hinge-line ; attached valve unknown ; upper valve 

 indistinctly auriculate, rather flat, irregular toward the margin with a small 

 pointed but not prominent apex, a little to the right of the middle of the hinge- 

 line ; sculpture composed of somewhat irregular radiating costse, not bifur- 

 cating but increasing by intercalation toward the margin, where they are much 

 crowded; these costae are formed by crowded overlapping rounded scales, like 

 biscuit piled one over another, and showing sharp edges only where worn ; 

 there are about forty with a somewhat smaller number of intercalary ones ; 

 the concentric sculpture is composed of ill-defined lines of growth, and the 

 whole surface is microscopically gT^nulose; interior polished, silvery, repro- 

 ducing the external rugulosities ; muscular impressions in\isible ; cartilage pit 

 triangulai', distinct, hinge-line smooth, margin nearly simple. Lon. of shell, 

 28.0; of hinge-line, 13.0 ; height of shell, 30.0 mm. 



Station. 227, off St. Vincent, in 573 fms., fine sand and gray ooze ; the bottom 

 temperature 40°.5 Fahrenheit. 



This shell has an unmistakably abyssal facics and seems to belong to the 

 genus Hinnites. It is named in honor of Prof. Charles B. Adams, of Amherst, 

 to whom so much of our knowledge of the fauna of the West Indies and 

 Panama is due, and who was among the first of American naturalists to recog- 

 nize the variability of what we call species, and the close relations which exist 

 in nature between forms admitted by naturalists to be of " specific " value, or, 

 in other words, which have obtained a temporary equilibrium of characters 

 which they transmit to their descendants. 



