96 Mr.R.J.L.Guppy on Diplommatina Huttoni in Trinidad. 
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 
species. 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- 
phoride, to which these characters attach it more closely than 
to the Cyclostomide. Its position, therefore, 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 Diplummatina 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 
