DALL: MOLLUSCA AND BRACHIOPODA. 429 
attenuated ; surface covered with almost microscopically minute granules arranged 
in radial lines except where removed by friction; the disk of the shell shows their 
scars on its otherwise polished surface. Lon. 5.7; alt. 5.3; diam. 4.4 mm. 
U.S. S. “Albatross,” station 3392, Gulf of Panama, in 1270 fathoms, hard 
bottom, temperature 36°.4 F. U.S. N. Mus. 122,931. 
A single specimen of this minute, thin species was obtained. It is so fragile 
that it is impracticable to open the valves, so the hinge remains undescribed. The 
shell has the surface of a Poromya; another specimen, apparently identical but 
larger, measures: lon. 9.5; alt. from the basal margin to hinge line, 7.5; total 
alt. 9.0; diam. 8.0 mm. In this specimen a single delicate flattened right car- 
dinal fits under the hinge margin of the left valve, while a long posterior lateral 
lamina in the latter underlies the right posterior hinge margin. These teeth 
differ from those of the typical Poromya in being thin and lamellar, but are simi- 
larly located. The second specimen is from the Ecuador coast, in 1132 fathoms, 
ooze, bottom temperature 36° F. U.S. N. Mus. 122,930. 
Dermatomya Datt. 
Dermatomya Dall, Proc. U. S. Nat. Mus., 1889, 12, pp. 289, 291; type, P. (D.) mac- 
troides Vall, /. c. p. 291, pl. 8, figure 8. 
Poromya (Dermatomaya) mactroides Dat. 
U. S.S. “ Albatross,” station 2781, southern coast of Chile, or western Pata- 
gonia, in 348 fathoms, mud, bottom temperature 49°.9 F. Type, figured in 
1889, U. S. N. Mus. 122,733. Also at stations 2783, in 122 fathoms, tempera- 
ture 48°, and 2785, in 449 fathoms, temperature 47° F. 
When this species was first described the description and figure were made 
from the type above referred to, of which the measurements were: lon. 10; 
alt. 8; and diam.7 mm. But a larger specimen turning up later, and being 
supposed to be an adult, the measurements were taken from that specimen which 
was from the coast of Ecuador. Now better specimens having become available, 
the large form proves to be distinct, and the measurements taken from it are 
therefore no longer applicable to P. mactroides and should be corrected accord- 
ingly, while the locality at station 2793, off the coast of Ecuador, should be ex- 
punged entirely so far as P. mactroides is concerned. It belongs to the next 
species. 
Poromya (Dermatomya) equatorialis Datt, n. sp. 
Plate 5, figures 1, 2. 
Shell subtrigonal, inflated, slightly inequivalve, white covered by a strong dark 
olive-gray periostracum, paler near the basal margin ; surface smooth except for 
