MAZATLAIf UNIVALVES 237 



enriched by 12 from Panama, (of whicli one. V. minuta, is a 

 Teinostoma, as is also the PNeritina pusilla from Jamaica of 

 the same author,) consists of a group of exceedingly mmute 

 turbinate or discoidal shells, differing greatly in shape, but 

 agreeing in colour and textiu'c, which are white and subhyaliue. 

 They have but few, rapidly enlarging whirls : the aperture is 

 generally much dilated and siuuated ; the umbilicus is almost 

 alwaj's large. They are either smooth and glossy ; or variously 

 ribbed, keeled or striated. In some respects they resemble 

 C.yclostrema, in others Adeorbis. Indeed many of the species 

 could not be separated genericall.y from the forms figured by 

 the author of the latter genus, Searles Wood, Crag Moll., pi. 15, 

 except by the texture. All the species examined agree in a 

 remarkable disproportion between the nuclear and the adult 

 parts of the shell. While the usual number of whirls is four 

 and a half, three of these are occupied with the unformed shell, 

 which is smooth in the sculptured species, and distinctly mark- 

 ed even in the glossy ones ; while only one, or one and a half, 

 (very rarely two,) suffice for the fuU grown portion. From this 

 cixcumstance it might have been supposed that they are aU 

 yoimg shells : but as they do not in the least resemble the 

 young of any larger Mazatlan species, and as more than 150 

 individuals were found, all keeping to the same type, it is 

 presumed that it indicates a peculiarity in the animal, which 

 may serve to distingu.ish it from neighbou.ruig genera. It is 

 exceedingly to be regretted that Dr. Gray should have used 

 the name over again last year for a genus of laud shells.* 

 Among the species described as Eotellae by D'Orbigny and 

 others (e. g. Globulus striatus, semi-striatus, pusdlus, carinatus 

 and anomalus) are perhaps several Vitrinellaj. Similar forms 

 are also known from the Eastern Seas, It is probable that 

 the existing species are extremely numeroiis, though the indivi- 

 duals are few. Although many of the Mazatlan specimens 

 were perfectly fresh from their native haunts, not a trace of 

 operculum was found. Of the described species, four are 

 shewn by the types in Mr. Cuming's collection to be common 

 to Panama and Mazatlan ; t fourteen appear now for the first 



• Dr. Gray proposes to alter the name of this latter genus to Vitrinula. 



t Besides these may be seen in the Cumingian collection types of V. valva- 

 toides and Teinostoma minutum from Panama ; and V. tincta, V. interrupta and 

 Ethalia megastoma from Jamaica. The latter, along with a young Natiea ?can- 

 rena, were found with the specimen of V. interrupta. The indented species, 

 ranked with this genus by its author on account of their teiture, accord better 

 with Ethalia or Teinostoma, and do not display the characteristic dilTerence 

 between the earlier and later whirls. 



