230 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



KEY TO THE SPECIES OF THE SUBGENUS SCALENOSTOMA. 



Aperture irregularly ovate rangii. 



Aperture regularly broadly ovate dotella. 



ODOSTOMIA (SCALENOSTOMA) DOTELLA, new species. 



Plate 30, fig. 5. 



Shell elongate-conic, vitreous, translucent. Nuclear whorls deeply 

 obhquely immersed in the first of the succeeding turns, above which 

 only the tilted edge of the last volution projects. Post-nuclear 

 whorls flattened, very strongly angulated at the periphery where they 

 are much wider than at the appressed summit. The summit of the 

 succeeding turns falls very much anterior to the angulated periphery 

 and gives to the whorls a decided overhanging appearance. Base 

 well rounded. Entire surface of spire and base marked by numerous, 

 almost vertical lines of growth and very many exceedingly fine spiral 

 striations. Aperture broadly ovate, posterior angle acute; outer lip 

 thin; angulated at the periphery; columella slender, very strongly 

 curved and slightly revolute. 



The type (Cat. no. 206934, U.S.N.M.) and six specimens were 

 dredged at U. S. Bureau of Fisheries stations 2826-2828, in 9J to 10 

 fathoms, off Ceralvo Island, Gulf of California. The type has six post- 

 nuclear whorls and measures: Length 2.3 mm., diameter 0.8 mm. 

 Cat. no. 206935, U.S.N.M., contains six specimens from U. S. Bureau 

 of Fisheries station 2823, off La Paz, in 26^ fathoms, broken shell 

 bottom, ofT Cacachitas, Gulf of California. These and the next are 

 provisionally referred here. One specimen from U. S. Bureau of 

 Fisheries station 2822, in 21 fathoms, off La Paz, Mexico (Cat. no, 

 206936, U.S.N.M.). 



ODOSTOMIA (SCALENOSTOMA) RANGII de Folin. 



Plate 30, fig. 2. 

 Cliemnilzia rnngii i>e Foijx, Les Mel&grinicoles, 1867, p. 61, pi. 6, fig. 1. 



Shell elongated-turrited, white. Nuclear whorls small. Post- 

 nuclear whorls flat in the middle, somewhat excurved at the summit 

 which is closely appressed against the preceding whorl immediately 

 anterior to the keel. Periphery of the last whorl marked by a very 

 strong acute lamellar keel. Base moderately well rounded. Aper- 

 ture irregularly ovate, posterior angle acute; outer lip thin, strongly 

 angulated at the periphery; columella curved and reflected; parietal 

 wall covered with a thin callus. 



De Folin's type comes from the Bay of Panama or Negritos Island. 

 It has twelve post-nuclear whorls and measures: Length 2.7 mm., 

 diameter 1.1 mm. 



