MUSEUM OF COMPARATIVE ZOOLOGY. 283 



Poromya (Ceto concha) elongata, n. s. 



Shell whitish, not pearly, somewhat resembling the preceding, but much 

 more elongated ; surface more densely and minutely granulate, tbe granules 

 being in even radiating series for the most part ; the lines of growth are 

 stronger and the surface not so smooth ; the epidermis is similar, but appar- 

 ently thinner ; the beaks are contiguous, and are less elevated, less spiral, and 

 less prominent ; the hinge-line, though longer, is thinner; the cardinal tooth 

 more acute and much smaller ; the shelf for the cartilage weaker, longer, and 

 narrower; the ridge extending backward from the beaks is not so near the 

 hinge-margin, and the area between is wider and obliquely cut oflF at its pos- 

 terior end, forming a more decided angle than in G. albida ; the anterior end 

 and base are elegantly rounded, but the posterior end is somewhat rostrated 

 with an obscure impression extending from the beaks to the lower posterior 

 rounded angle of the rostration ; the beaks are nearly equidistant fror.i the 

 ends, but probably a little behind the median line ; the hinge-margin in the 

 right valve is a little expanded before the beak. Lon. 22.5 ; alt. 17 ; diameter 

 of right valve 6.25 ; of shell, probably, 12.5 mm. 



A single right valve was obtained by the " Blake" at Barbados, in 100 fms.; 

 and a living specimen by the U. S. Fish Commission at Station 2337, north- 

 west of Cuba, in 199 fms. It has somewhat the shape of Poromya neceroides 

 Seguenza, but the hinge differs. The soft parts are described in the sub-generic 

 diagnosis with some additional notes under the next species. The lower palpi 

 are absent, and the gill rows one on each side, adjacent, but not touching, at 

 the point of origin without any appendix. 



Poromya (Cetoconcha) bulla Dall. 



Lyonsia bulla Dall, Bull. M. C. Z., VI. p. 61, 1878 ; IX. p. 107, 1881. 



(?) Thracia nitida Verrill, Trans. Conn. Acad., VI. p. 221, pi. xxxii. fig. 22, 1884. 



Habitat. Station 31, Gulf of Mexico, in Lat. 24° 33' N., Lon. 84° 23' W., 

 1920 fms., living, bottom temperature 39°. 5 F.; U. S. Fish Commission (as 

 Thracia nitida), off Chesapeake Bay, in 1917 fms. 



The agreement between Professor Verrill's figure and description on the one 

 hand, and the Blake specimens on the other, is so close, that I can hardly 

 doubt they are the same species, though I have not examined specimens of his 

 shell. The soft parts of this species are much the same as in C. elongata, ex- 

 cept that the retractile siphon is proportionately longer, and the gill series 

 consists of two short rows (5-7 lamellse) on each side radiating forward from 

 a point immediately behind the foot. The lower palpi are present but not 

 branchial; but on the body surface near them are two short rows (8-10 sec- 

 tions or lamellse), one on each side, diverging backward, the anterior end of 

 each being under or behind the lower palpus of that side. The trend of these 



