dall: mollusca and brachiopoda. 347 



the periphery, and numerous finer, obscure, spiral lirulae over the rest of the sur- 

 face; aperture extremely oblique, outer lip produced along tlie suture, retrac- 

 tively arcuate between suture and periphery, produced and patulous at the 

 periphery, thence obliquely arcuate to the base of the pillar ; it is everywhere 

 simple, smooth, not reflected, but loaded with a heavy layer of callus, ■which is also 

 spread evenly and smoothly over the body and about two-thirds of the base ; 

 pillar extremely short, flattened, produced in a single large, flattened, heavy tooth, 

 ■with a deeply excavated notch between the tooth and the anterior margin of tlie 

 aperture; the callus entirely covers and conceals the umbilical depression if any 

 existed. Height, 7.0; of aperture, 3.5 ; max. diam. about 15.0 mm. 



U. S. S. " Albatross," station 3396, Gulf of Panama, in 259 fathoms, mud, 

 bottom temperature 47°.4 F. U. S. N. Mus. 122,954. 



The interior of the shell was once pearly, but has been dulled by decay. It is 

 impossible at present to say whether the broad mass of callus on the base was 

 originally opaque white or pearly. 



GAZA Watson. 



Gaza Watson, Journ. Linn. Soc., 1870, 14, p. 601 ; Challenger Report, Gastropoda, 

 1885, p. 93; type, Gaza daedala Watson, op. cit. 



Gaza rathbuni Dall. 



Plate 2, figure 4 ; plate 3, figure 6. 



Gaza rathbuni Dall, Bull. Mus. Comp. Zool., June, 1889, 18, p. 354 ; Proc. U. S. 

 Nat. Mu8., 1889, 12, p. 342, pi. 7, fig. 4 (immature). 



U. S. S. " Albatross," station 2818, near the Galapagos Islands, in 392 fathoms, 

 sand, bottom temperature 44° F. Also at station 3402, in 421 fathoms, ooze, 

 temperature 42°. 3, in the same vicinity. U. S. N. Mus. 122,955. 



The original specimen was immature, not having formed the reflected Up. The 

 species has therefore been rcfigurcd from the present material. 



An additional note may be made that the nuclear whorls of all the species of 

 Gaza which I have examined have a membranous consistency, so that when the 

 shell has dried the nucleus shrivels up and drops off, leaviug a cyliudrical perfora- 

 tion which is continuous with the umbilicus. 



The dimensions of the adult shell are : alt. 32 ; of last wliorl, 28 ; of aperture, 

 (vertical), 23 ; max. diam. of base, 45 ; min. diam. 38 mm. 



The periostracum is olivaceous, polished, very thin, and readily dehiscent. In 

 Watson's type it had, doubtless, been lost, thus accounting for his observation 

 that it was wanting in G. daedala. 



This genus affords, perhaps, the most exquisite gems of the abyss.il shell fauna; 

 in shape and iridescence nothing more lovely can be inuigined. 



