490 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
the narrow spaces between the scarcely developed ribs are pale brown; the beaks are purple, clouded. 
The interior is much the color of the yolk of an egg, with purple cloudings at the cavities of the beaks. 
Length, 40; height, 45; diameter, 32 mm. 
Mayaguez Harbor, Porto Rico, stations 6058 and 6061. 
Genus PROTOCARDIA Beyrich, 1845. 
Sculpture radial anteriorly; posterior area with reticulate or spinose sculpture; shells thin and 
usually small ; foot carinate. 
Protocar dia peramabilis Dali. 
Cardium peramabile Dali, Bull. Mus. Comp. Zoo!, Cambridge, ix, p. 132, 1881; Bull. Mus. Comp. Zoo!, Cambridge, xn, 
p. 269, pi. IV, fig. 7, 1886. 
Shell small, slightly inequilateral, rather thin and fragile, inflated; posterior area sculptured 
with a great number of line, radiating, nearly smooth ribs, the spaces between them being slightly 
pitted, the whole being covered with a fine epidermis, which is scaly on the ribs; the anterior three- 
fifths of the shell is sculptured with equally line, radiating ribs, and these are crossed by very 
numerous somewhat fainter, concentric ridges, leaving the surface everywhere minutely beaded; 
borders of the shell delicately and sharply serrate, not gaping; within the shell the outside patterns 
of sculpture may be plainly seen. Color whitish. 
Length, 10; height, 11; diameter 9 mm. 
Mayaguez Harbor, Porto Rico, two shells; Aguadilla, one worn valve. 
The foot is keeled below but not serrate. 
Protocardia tincta Dali. Plate 58, fig. 4. 
Cardium peramabile vav. tinctum Ball, Bull Mus. Comp. Zool, Cambridge, xn, p. 270. 1886. 
Shell small, fragile, nearly equilateral, considerably inflated; posterior area sculptured with 
minute, radiating ribs; every second, third, fourth, or fifth one bears a row of sharp, elevated spines 
or scales; the spaces between these ribs are crossed by delicate scales, making them pitted; the 
remainder of the shell is sculptured with very finely beaded ribs, as in P. peramabilis; borders of the 
shell finely and sharply serrate, not gaping; outside sculpture showing faintly within; anterior 
laterals showing as long arched ridges within, entering far within the cavity of the beaks. Color 
whitish, beautifully tinted and clouded with pink or red. 
Length, 13; height, 12; diameter, 9 mm. 
Mayaguez Harbor, Porto Rico, in 25 to 30 fathoms. Quite a number of valves were taken. 
This beautiful form is certainly distinct from P. peramabilis. It is not so high in proportion to 
its width, is a little less inflated, the line between the two areas of sculpture is not so distinctly 
marked out, and when perfect it has the scaly spines on the posterior area finely developed. The 
anterior lateral teeth are different from those of P. peramabilis. 
Family THYASIRID^. 
Genus THYASIRA Leach, 1818. 
Shell thin to subsolid, subglobular, earthy; beaks turned forward; posterior side furrowed; lunule 
absent; ligament placed in a groove in the hinge line, partly external; hinge edentulous; muscular 
impressions superficial, elongated; pallia! line simple; borders of the shell closed, simple. 
It is Cryptodon and Axinus of authors. 
Thyasira trisinuata d’Orbigny. 
Lucina trisinuata d’Orbigny, Moll. Cubana, n, p. 300, pi. xxvii, figs. 46^9, 1846. 
Cryptodon obesus Veri-ill, Am. Journ. Sci., ill, p, 287, pi. 7, fig. 2, 1872: Trans. Conn. Acad. Sci., Ill, p. 11, p! 1, fig. 11 (not of Sars). 
Shell rather small, scarcely subsolid, inflated, higher than long, somewhat produced at the 
middle of the base; beaks high and rather full, turned forward over a feebly developed lunule; posterior 
slope with two deep, distinct, radial grooves; surface finely, concentrically striated; ligament lodged 
in a groove in the edentulous hinge; back cavities rather deep. Color white throughout. 
Length, 12; height, 14; diameter, 10 mm. 
Mayaguez, Porto Rico, several immature, worn valves, which appear to be of this species. 
Thyasira conia n. sp. 
Shell small, thin, rather compressed, inequilateral, the anterior end longer, somewhat impressed 
above, the posterior high and arcuate above, abruptly truncate in front, base rounded; shell white, 
