Cyclostrema, Adeorhis, Vitrinella, and related genera. 121 



imperforate, but with a depression bounded by a riblet in the um- 

 bilical rib (region ?) outside of the columella ; whorls few with a 

 thin fugacious epidermis ; outer lip thin ; pillow without teeth, pro- 

 jection, or folds, passing smoothly into the anterior margin." 



Type, D. modesta Dall. 



" This little shell will not fit into any of the groups defined in the 

 text-books, resembling more than any other group the Rotellidae, 

 from which it differs in wanting the sutural fasciole, the nacreous 

 layer, and the basal callus, as well as in possessing an epidermis. 

 It is remarkably solid for its size, and of a peculiar opaque white- 

 ness, like Mamma among the Naticidae," Bull. Mus. Comp. Zool., 

 xviii, p. 362, pi. xxi, figs. 3, 3a, 1889. 



This was proposed as a subgenus of JEthalia, but it is question- 

 able if the species referred to that genus by Mr. Dall could right- 

 fully belong to it, when taken in its most restricted sense. In 

 some features it comes near the subgenus Ganesa Jeffreys. See 

 pp. 114, 116. 



The following genera have been classed with the Cyclostrematidae 

 by Fischer and Tryon. In several features, their types seem much 

 nearer the genus Liotia Gray and related genera, than any of those 

 of the preceding group. 



Microtheca A. Adams, 1863. Type, M. crenellifera A. Ad. Japan. 



Globosely turbinate ; peritreme continuous; umbilicus wide, crenu- 

 lated. Operculum unknown. Ann. Mag. X. H,, xi, p. 265, 1863. 

 Figured in Thes, Conch., copied by Tryon. 



Haplocochlias P. P. Carpenter, 1864. Type] H. cycloplioreus Carpenter. Lower 

 California. 



Similar to a Collonia but not margaritaceus, with a continuous 

 thickened peritreme having an exterior varix ; young umbilicate, 

 adult lacunate. Animal and operculum unknown. Ann. Mag. N. H., 

 xiii, p. 476, 1864. 



Leucorhynchia Crosse, 1867. Type, L. Caledonica Crosse. New Caledonia. 



In the peculiar callous rostrum prolonged past the umbilical 

 region, this genus approximates to Craspedostoma Lindstrom. 

 Journ. de Conch., xv, p. 319, pi. 11, f. 4, 1867. 



