the Cyclostomacea of Eastern Asia. 447 



Viv. p. 16) * to be C. variegatus, Swains., and C.planorbulus, Lam., 

 both from the Philippines. These shells possess a closely wound, 

 thick operculum, membranaceous internally and subtestaceous 

 without, very similar indeed to that of Opisthoporus, except that 

 the latter is hollow within — a distinction the importance of 

 which may be over-estimated. There is a deep sulcation round 

 the margin, and considerable concavity externally. The shell is 

 smooth or nearly so, very depressed, subdiscoidal, with a thick 

 epidermis, and is generally precisely similar to the discoidal 

 forms of Ci/clophorus (e. g. C. stenostomus, Sow.), and especially 

 to certain Burmese species (as C. calyx, Bens.), to which the 

 Cycloti are doubtless very closely allied. The other Philippine 

 species (C. mucronatus, Sow., C. pusillus, Sow., C. scalaris, Pfr., 

 C. substriatus, Sow.) will be classed in the restricted genus, 

 which doubtless comprises also the three Chinese species, as 

 well as those of Cochin-China, Java, Borneo, &c., and several 

 from the Moluccas, lately described by Dr. von Martens in the 

 ' Malakoz. Blatter.' The nearest allies of the genus thus re- 

 stricted being apparently amongst the species of Cydophoms, 

 Cyclotus must be referred to the same subfamily as that genus. 



IV. C. Macgillivrayi, Pfr., from the New Hebrides, may very 

 possibly be a depressed form of the type for which Dr. Gould 

 has proposed the generic name Ostodes. The operculum is 

 subtestaceous, but otherwise in no respect different from that of 

 some Cyclophori. C. daucinus, Pfr., and C. Recluzianus, Pfr., 

 from the Solomon Islands, may be related; but these species are 

 only known to me by description. 



V. Omitting a few dubious species, there only remain the 

 four Indian forms, and C. conoideus, Pfr., from the Seychelles 

 and Mauritius, which very probably belongs to the same type as 

 C. semistriatus. These species are nearly affined to Lithidion, 

 but differ in their concentric operculum, and, being well distin- 

 guished from all known genera, must be classed by themselves. 

 I propose to call them 



Cyclotopsis, n. g. 



Testa late umbilicata, depressa v. turbinato-depressa, spiraliter 

 lirata ; apertura subcirculari. Operculum concentricum, multi- 

 spirum, duplex, interne membranaceum, externe testaceum, margini- 

 bus anfractuum externis elevatis. 



Animal Cyclostomatis, baud Cyclophori. 



Type, C. semistriatus, Sow. 



This genus will be classed as a subgenus of Cyclostoma hy all 

 who consider Otopoma and Lithidion as such. It may, as above 

 suggested, be related to Aperosioma. In the raised margins of 



* I have not access to the original work at present. 



