188 BULLETEN 181, UNITE© STATES NlATIiO!NlA)L MUSEUM 



APEROSTOMA (INCIDOSTOMA) MALLEATUM, new species 



Plate 25, Figures 4-6 



Shell large, very depressed-helicoid. The early whorls pale brown, 

 the last 1.5 turns pale chestnut brown, with the posterior half of 

 the first dark chestnut-brown and the anterior half and umbilical 

 wall of about the same shade as the upper side of the last turn. 

 There is a pale narrow peripheral line below which a narrow almost 

 black band is present. The nucleus consists of 2 turns, which are 

 small, well rounded, and smooth. The succeeding turns are well 

 rounded and marked by decidedly retractively slanting axial riblets, 

 which on the last 1.5 turns become irregular in strength and spacing. 

 On this part of the shell the upper surface, too, shows irregular 

 malleations. The suture is strongly impressed. The summit of the 

 last whorl is slightly deflected. Periphery feebly angulated. Base 

 openly umbilicated, somewhat inflated, strongly rounded, and marked 

 by the continuation of the axial riblets, which become very materially 

 strengthened on the umbilical wall, where they form rather rough 

 strong ribs. The base also and umbilical wall show the malleations 

 referred to for the spire. Aperture circular, except the posterior 

 angle, where the outer lip is reflected backward to form an incom- 

 plete siphon, which extends some distance beyond the periphery and 

 is separated from the preceding turn by a mere slit. There is a 

 profound sinus in the peristome at the posterior angle. Peristome 

 thickened, almost double on the inner lip and thin on the outer and 

 basal lip. Operculum typically aperostomid, of about 9 whorls. 



The type, U.S.N.M. No. 317578, comes from the Evezard collection. 

 It is without locality. It has 4.7 whorls and measures : Height, 24.8 

 mm.; greater diameter, 48 mm.; lesser diameter, 34.5 mm. Height 

 of aperture, 15.8 mm. ; diameter, 21.2 mm. 



We hesitate to describe a species without definite locality, but 

 because the strong malleations of this species differentiate it from 

 all other forms before us, we feel it merits recognition. 



APEROSTOMA (INCIDOSTOMA) PERGRANDIS (Kobelt) 



PiATE 25, Figures 1-3 



1912. Neocijclotus perffrandis Kobelt, Martini-Chemnitz Conchylien Cabinet, 



vol. 1, sect. 19, pt. 3, p. SS7, pi. 132, figs. 4-6. 

 1923. Poteria {Neocijclotus) pergrandis H. B. Baker, Occ. Pap. Mus. Zool. Univ. 



Michigan, No. 137, p. 30. 



We have not seen this species and so give a translation of Kobelt's 

 description : 



Shell apparently the largest of the genus, openly, broadly umbili- 

 cated, depressed, thick-walled, coarsely striated with oblique, irregu- 



