214 BULLETIN OF THE 



adult; in very young specimens they are absent, and the shell can hardly be 

 distinguished from P. imhrifer, which has commonly been confounded with it, 

 as mentioned under that species. The present one is characterized by the very 

 large shelly bubbles, generally worn away, and leaving their semicircular basal 

 edges plainly visible in fifteen to eighteen series, with intercalary ones near 

 the margin. The umbo of the upper valve has sharp elevated concentric 

 ridges without pustulations. There are inside near the margin of adult shells 

 17-21 short liroe, thickest at their distal ends usually and not extending into 

 the hollow of the shell, except the marginal ones, and these not always. The 

 shell is very thin, vitreous, and pale yellowish in color. 



Amusium (Propeamusium) Holmesii Dall. 



Plato V. Figs. 5, 11. 



Shell small, somewhat obli([ue, thin, brightly colored (like A. var. ma.rmo- 

 ratum), the convex valve with twenty to twenty-eight faint radiating ridges, 

 absent toward the beaks and with intercalary ridges toward the margin ; inter- 

 spaces between the ribs polished, mostly smooth or with traces of concentric 

 lamellae which near and over the radiating ridges rise to arched scales, which 

 in some cases are closed in front, forming spindle-shaped pustules, with the 

 longer axis in the concentric line to which they belong ; anterior ear the larger, 

 pectinately scaled on the margin, with obscure radiating or lamellar sculpture ; 

 concave valve finely concentrically waved, the waves becoming crowded and 

 scaly toward the margin ; anterior ear with three or four radiations and strong 

 lamellae, posterior ear lamellate, but not radiated ; anterior margin rounded, 

 posterior ditto, produced. Alt. 12.0, Ion. of shell 12.0, of hinge line 6.0, 

 max. diam. 2.0 mm. Internal liraj eleven to fourteen, fine, with a tendency 

 to pair, and falling considerably short of the margin in the completely adult 

 shell. 



Dredged at Station 273 in 10,3 fms., and in 100 fms. at Barbados, living. 

 The bottom was yellow coral and broken shell, and the temperature 59°.5 F. 



This pretty shell is nearest A. Hoskynsi Forbes, from which it differs by the 

 polished umbonal region, the larger number of ribs, the smaller size and differ- 

 ent shape of the pustular scales, by its larger size, differently proportioned 

 and pectinated ears, and by the strength, number, and character of its internal 

 lirse. Its form is nearest that of A. Pourtalesianum, var. marmoratum, which 

 is also brightly colored. It is named in honor of Dr. Holmes, the author of 

 the "Pliocene Fossils of South Carolina." 



Amusium (Propeamiusium) Sayanum Dall. 



Plate V. Figs. 3, 9. 



Shell compressed, nearly equivalve, somewhat inequilateral ; white ; ^nth 

 dissimilarly sculptured valves ; right valve with (near the middle) about 



