dall: mollusca and brachiopoda. 237 



yellowish, nearly transparent, polished ; sculpture of (on the penultimate whorl 

 four) sharp distant spiral, fine, microscopically punctate, incised lines ; these in- 

 crease on the last whorl to about fifteen, of which five or six on the base are 

 closer, tlie remainder, on the sides of the whorl, are less crowded, subequidistant, 

 and similar; shell obscurely parallel-sided, slightly rounded, with a rounded and 

 shghtly protracted base ; aperture narrow, rounded in front ; the outer lip sharp, 

 simple, or minutely notched by the incised spiral lines ; body with a slight wash of 

 callus ; pillar straight, short, with a single obscure fold near the middle, which lags 

 behind the aperture; there is no umbilical perforation. Lon., 70+ ; max. diam., 

 4.5 mm. 



U. S. S. "Albatross," station 3392, in the Gulf of Panama, in 1270 fathoms, 

 hard bottom, bottom temperature 36°.4 F. U. S. N. Mus. 123,074. 



No species at all similar is reported from this part of the world, and hence, 

 though the spire is imperfect, it has seemed best to name it. 



Acteon (Microglyphis) mazatlanicus Dall, n. sp. 



Plate 5, figure 7. 



Shell small, polished, white, acute, five-whorled, the spire shorter than the aper- 

 ture ; nucleus glassy, small, sinistral, mostly immersed in the following whorl ; 

 suture distinct, not channelled or appressed ; early whorls moderately rounded, 

 with extremely faint traces of spiral striation or smooth; last whorl obscurely 

 angulate at the shoulder, above which the whorl slopes flatly toward the suture, 

 remainder of the wliorl evenly ovately rounded ; sculpture of extremely fine, sharp, 

 close-set spiral striae, with a tendency to pair, slightly less crowded behind the 

 shoulder aud more crowded on the base near the pillar ; these striae are crossed 

 by faint, irregularly distributed, slightly raised lines of growth, aud are more or 

 less microscopically puuctate; periostracum imperceptible; outer lip thin, sim- 

 ple, sharp, slightly patulous toward the middle, and receding near the suture; 

 pillar arcuate, truncate obliquely, aud with two strong spiral plaits, the anterior 

 of which is seated on the edge of the truncation and is continuous with a distinct 

 notch at the end of the pillar, around wliicii it passes imperceptibly into the mar- 

 gin of tlie lij) ; body with a faint wash of callus ; base imperforate. Lon., 5.5 ; of 

 spire, 2.3 ; max. diam., 3.0 mm. 



U. S. S. " Albatross," station 3131, in 995 fathoms, mud, off Mazatlan, Mexico, 

 bottom temperature 37°.0 F. U. S. N. Mus. 123,075. 



This species is more acute and more closely sculptured than J. (-1/.) breviculux 

 of the California coast, while the spire is more acutely pointed and the spiral 

 sculpture more close-set than in A. (.V.) prrconinis, which approaches it more 

 closely than either of the other known species of this subgenus. 



The group is apparently characteristic of the West American coast from Cali- 

 fornia to Cape Horn, but will probably be found elsewhere, in great depths of 

 water. 



