96 Mr. R. J. L. Guppy on Diplommatina Huttoni in TrinidacL 



dental membrane. Owing to its minuteness and tenuity, the 

 operculum is scarcely visible to the naked eye, even when iso- 

 lated. It is horny, transparent, subcircular, and composed of a 

 few indistinct whorls with raised edges, hardly resembling the 

 figure I have seen of that of D. folliculus. 



The species is remarkable as being the only sinistral one of 

 the genus, which only includes, I believe, five or six known 

 spec'ies. The lingual dentition, being very minute, is somewhat 

 difficult of preparation ; but I have been able to make out its 

 characters, which are as follows : — The dental band is of mode- 

 rate length ; the teeth are 3.1.3, the median is broad, its 

 edge narrowly reflexed and five-toothed, its base narrow, almost 

 pointed. The first and second laterals are subclavate, their 

 edges reflexed and three-toothed. The third lateral is somewhat 

 hamate and obscurely tricuspid. The mandible is broad and 

 flat, covered with very distinct, separate, lozenge-shaped plates. 

 All this tends to induce one to retain this genus in the Cyclo- 

 phoridfe, to which these characters attach it more closely than 

 to the Cyclostomidse. Its position, thei'cfore, with respect to 

 its congeners seems to have been pretty correctly given by 

 Pfeiffer and Gray. 



The occurrence in Trinidad of a second land-shell common to 

 India naturally induces one to seek an explanation of so curious 

 a circumstance. Ennea bicolor has for some years been known 

 to be common to St. Thomas and Trinidad in the West Indies, 

 and to the East Indies. But it would have been unsafe to 

 ground any conclusion upon a single coincidence, which might 

 have been due to accident, as Mr. Bland appears to have sug- 

 gested. Ennea bicolor is rare in Trinidad. During my eight 

 years' residence in Trinidad, I have closely searched every loca- 

 lity near Port-of-Spain ; and until made aware by Mr. Bland of 

 its existence here, I had not discovered Diplommatina Huttoni. 

 It has not been found in any other place than near the Maracas 

 Waterfall, a distance of nine or ten miles from Port-of-Spain, 

 the nearest seaport. I think, therefore, it is highly unlikely 

 that these two species can have been introduced, not to mention 

 the improbability of their surviving a voyage from India. In 

 fact I need scarcely say more on this point, considering that the 

 only direct communication between Trinidad and India is con- 

 fined to the ships which bring Asiatic labourers from the latter 

 place. I would suggest for consideration the possibility of these 

 species having migrated by means of the supposed tertiary 

 Atlantis, of the former existence of which I have endeavoured to 

 show the probability in my paper on the Tertiary formations of 

 the West Indies, published in the twenty-second volume of the 

 Quarterly Journal of the Geological Society. It is true that 



