dall: mollusca and brachiopoda. 429 



attenuated ; surface covered witii almost microscopically minute granules arranged 

 in radial liues except where removed by friction ; the disk of the shell shows their 

 scars on its otherwise polished surface. Lou. 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 tlie valves, so the hinge remains undescribed. The 

 shell has the surface of a Poromya ; another specimen, apparently identical but 

 larger, measures -. Ion. 9.5 ; alt. from the basal margin to hinge line, 7.5 ; total 

 alt. 9.0; diam. 8.0 mm. In tlris specimen a single delicate flattened right car- 

 dinal lits under the hinge margin of the left valve, while a long posterior lateral 

 lamina in tlie 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. 



Derniatoinya Dall. 



Dermatomya Dall, Proc. U. S. Nat. Mus., 1889, 12, pp. 289, 291 ; type, P. (D.) mac- 

 troides Dall, /. c. p. 291, pi. 8, figure 8. 



Poromya (Dermatomaya) mactroides Dall. 



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 : Ion. 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 wliich 

 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 therefore no longer applicable to P. mactroides and should be corrected accord- 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 Dall, n. sp. 



Plate 5, flKurcg 1, 2. 



Shell subtrigonal, inflated, slightly inoquivalve, white covered bv a strong dark 

 olive-gray periostracum, paler near the basal margin ; surface smooth except for 



