282 CYCLOSTOMID^. 



Megalomastoma, Guilding. 



Syn. — Lomastoma, Woodward. 



Distr. — 29 sp. W. Indies, E. Indies, India, Madagascar, Mau- 

 ritius. Fossil. Eocene — . Paris and Isle of Wight. M. Antil- 

 larum., Sowb. (Ixxv, 59). 



Shell oblong or pupa-shaped, scarcely perforated, aperture 

 circular. OjDerculum thin, horny, many-whorled, flat. 



FARCiMEN, Troschel. Lip thickened. W. Indies. M. ventri- 

 cosum, d'Orb. (Ixxv, 60). 



MEGALOMASTOMA, Guild. Lip rather thin. W. Indies. 



COPTOCHEILUS, Gould. Narrowly perforate ; aperture slightly 

 touching or not touching the body-whorl ; peristome not thick- 

 ened, more or less duplicate. E. Indies. Scarcely distinct 

 from Megalomastoma (restricted). M. altum^ Sowb. Philippines. 



TOMOCYCLUS, Crosse and Fischer. Shell perforate, turreted, 

 truncate ; aperture subcircular, small ; peristome duplex, the 

 inner margin direct, the outer margin widely expanded, excised 

 above. Operculum with a median posterior rounded process, 

 margins of the whorls sublamellate. Central America, Guat- 

 emala. M. simulacrum, Morel. (Ixxv, 61). 



Hainesia, Pfeiffer, 1856. 



Syn. — Mascaria, Angas. 



Distr. — 4 sp. Madagascar, Siam. H. Myersi, Haines. 



Shell oblong-turreted, whorls convex, without epidermis, re- 

 sembling Megalomastoma. Operculum angular, paucispiral. 



DACRYSTOMA, Crosse and Fischer, 1871. Whorls flattened, 

 with very thin, deciduous epidermis. H. arboreum^ G. and F. 

 Madagascar. 



DiPLOMMATiNA, Bcnson. 



Distr. — 100 sp. India, East Indies, Australia, Polynesia. 

 D. folliculus^ Pfr. (Ixxv, 62, 63). 



Shell suboval, costulate, dextral or sinistral, thin, scarcely 

 perforated; aperture subcircular; peristome double, outer margin 

 expanded. Operculum horny, multispiral. The eyes are situated 

 on the hind-part of the tentacles, at their base, and are composed 

 of two lobes, one lobe deeply seated in the tentacle and larger 

 than the other lobe, which is a small black point coming to the 

 surface on the outer side of the larger lobe. The generic name 

 is derived from this peculiarity of the eyes. 



PAXiLLUS, H. and A. Adams. Shell small, pupiform, sinistral, 

 rimate ; spire pointed ; aperture semiovate, ascending on the body- 

 whorl ; inner lip spreading, 1-plaited, outer lip expanded, notched 

 in front ; umbilicus defined by a rib. D. rubicunda, Martens 

 (Ixxv, 64). 



DiANCTA, Martens. Penultimate whorl constricted. D. coti-. 

 striata, Martens (Ixxv, 65, 66j. 



