264 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



AMPHITHALAMUS INCLUSUS Carpenter. 



AmpMthalamus indusus Carpenter, Ann. Mag. Nat. Hist., ser. 3, vol. 15, 1865, 

 p. 181. 



Shell elongate-ovate, purplish brown with the nuclear whorls 

 yellowish white. Nuclear whorls about one and one-half, well- 

 rounded, marked by about 15 slender, equal and equally spaced, 

 spiral threads and numerous, very fine, axial threads, lending tlie 

 surface a very minutely-pitted appearance. Post-nuclear whorls 

 subtabulatedly shouldered at the summit, well rounded on the 

 middle, marked by fine lines of growth only. Suture well impressed. 

 Periphery of the last whorl marked by a rather broad, low, rounded, 

 spiral thread, which is separated from the space posterior to it by a 

 narrow, shallow, spiral sulcus. Anteriorly, this cord passes, without 

 demarcation, into the general surface of the moderately long and 

 gently rounded base. Base broadly umbilicated, having a rather 

 broad, low, spiral cord a little posterior to the in- 

 sertion of the columella. Aperture oval, very 

 oblique, reenforced within by an iimer peristome 

 which, in the anterior portion of the outer lip, fuses 

 with it, while the columellar portion and the pa- 

 rietal portion stand at a considerable distance from 

 the columella and the parietal wall, being connected 

 with these by a concave bridge of shelly matter; 

 columella moderately long and stout. 



Doctor Carpenter's cotypes, three specimens (Cat. 

 Fig. 2.— amphithala- No. 15573, U.S.N.M.), come from San Diego, Cali- 

 Mus INCLUSUS Car- ^ -^ rpj^^ largest of these has two and one-half 



PENTER. o 



post-nuclear whorls, and measures: Length 1.4 mm., 

 diameter 0.9 mm. Cat. No. 105464, U.S.N.M., contains two speci- 

 mens, also from San Diego, and Cat. No. 213540, U.S.N.M., contains 

 one, from Catalina Island, California. 



AMPHITHALAMUS TENUIS, new species. 



Shell elongate-ovate, dark greenish horn-color, with the columella 

 and the aperture yellowish white, excepting the dark edge of the 

 peristome. Nuclear whorls one and one-half, well rounded, marked 

 by about 15 slender, equal and equally spaced, spiral threads and 

 numerous, very fine, axial threads, lending the surface a very mi- 

 nutely-pitted appearance. Post-nuclear whorls very narrowly sub- 

 tabulatedly shouldered at the summit, well rounded, smooth except- 

 ing fine, incremental lines. Suture moderately impressed. Periph- 

 ery of the last whorl well rounded. Base long, well rounded, bearing 

 a low, broad, spiral cord on its middle, wliich bounds the posterior 

 termination of the white area. Aperture oval, very oblique; peris- 



