DALL: MOLLUSCA AND BRAOHIOPODA. 415 
Protocardia panamensis DALL, n. sp. 
Plate 18, figure 1. 
Shell small, very pale brown or dirty cream color, equivalve, subequilateral, 
Plump, with elevated subprosocoelous beaks and a narrow thin ligament; sculp- 
ture, except on the posterior area, of small, flat, subequal radial ribs with nar- 
Tower channelled interspaces crossed by numerous small, equal, and equally spaced 
Concentric lamellae which do not rise above the ribs and are confined to the inter- 
Spaces ; on the average there are about thirty-three of the ribs with a smooth cordate 
lunular space in front of the beaks ; the posterior area begins with a rib bearing 
minute Spinules which are usually lost, leaving merely traces of their presence, 
behind this 21-23 similar ribs, narrower and slightly more elevated than those on 
the disk, with wider interspaces erossed by thinner and sharper concentric lamellae 
than on the disk; three or four of these interspaces instead of lamellae have 
Minute, widely spaced spinules easily and usually lost, at the rate of about one 
spinule to four lamellae; these rows of spinules are not uniformly distributed on 
different individuals; a broad, smooth swollen fold borders the posterior hinge 
line ; hinge normal, strong ; interior polished, whitish ; margin sharply serrate by 
ble Sculpture; the posterior area covers about one-fourth of the disk. Lon. 13.5; 
alt. 13.5; diam, 9.0 mm. 
U. 8. 8, « Albatross,” station 3355, Gulf of Panama, in 182 fathoms, mud, 
bottom temperature 549.1 F. U. S. N. Mus. 122,928. 
A rather simple and uninteresting little species with no particularly salient 
characters, 
Isocardiacea. 
Vesicomyacidae. 
VESICOMYA Darr. 
} Callocardia (A. Adams, 1864) E. A. Smith, Chall. Rep., Lam., 1885, p. 157. 
*sicomya Dall, Bull, Mus. Comp. Zoól., 1886, 12, p. 272; 1889, 18, p. 439. Type, 
Callocardia (1) atlantica Smith, op. cit., pl. 6, fig. 8. 
ardia (subgenus Vesicomya) Dall, Proc. U, S. Nat. Mus., 1895, 17, p. 693; 
1896, 18, p. Ii 
Calloc 
in character of the gill-filaments in this genus, as displayed in F. 
Sew 7 enc eee necessary to separate it from association with the Isocardi- 
the es E n into the iubet of Callocardia — showed that, 
i tank r y velongs to the Poe The subgenus of ig was elevated to 
7 locate ies in 1895 (Trans. Wagner Inst., 3, p. 551) under the name 
doubtful a cn nos the true relations of Vesicomya were still regarded as 
blas] ea y further study and more material showed the relationship of the 
1comya and the so-called Callocardia, rendering it necessary to unite 
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