366 BULLETIN OF THE 
small, oval, posterior, concealing a shell: no longitudinal furrows above the 
margin of the foot, and no caudal mucus pore: distinct locomotive disk ? 
external respiratory and anal orifices on the right anterior margin of the 
mantle ; orifice of combined genital organs behind and below right eye-peduncle. 
Shell internal, sigaretiform, rudimentary, small, flat, oblong, subspiral, 
nucleus infero-posterior. 
Jaw ribbed. 
Lingual membrane ——? 
Brazil. 
Until the jaw and dentition be known, its position is uncertain. The former 
from one of Férussac’s figures seems to be costate. 
For figure of animal, see Férussac, Hist., Pl. VII. A. 
From Feérussac’s figure 4 it appears probable that the shell may be more 
properly described as external, but covered by an accessory process of the 
mantle. 
Cryptostrakon, W.G. Binn. Animal limaciform, subcylindrical, atten- 
uated behind ; tentacles simple : mantle slightly anterior, thin, small, conceal- 
ing the shell ; no longitudinal furrows above the margin of the foot, and no 
caudal mucus pore : distinct locomotive disk ? external respiratory and anal 
orifices on the right central margin of the mantle : orifice of genital organs ? 
Shell internal, sigaretiform, rudimentary, large as mantle, membranous, sub-— 
spiral, with postero-lateral nucleus. 
Jaw ribbed. 
Lingual membrane with tricuspid central teeth, bicuspid laterals, and quad- 
rate marginals. 
Costa Rica. 
_ For figure of animal, internal shell, jaw, and lingual dentition, see Ann. of 
INERYEV AtcadssNatocin alowed txele 
Geeotis, SHutrn. Animal limaciform, with greatly expanding, flat sides: 
tentacles simple : mantle with an appendiculate process on the right posterior 
margin under the spire of the shell, which is internal, concealed before by a 
reflection of the mantle, and behind is imbedded in the mantle: longitudinal 
furrows ? caudal pore ? distinct locomotive disk? external respira- 
tory and anal orifices at the right posterior margin of the mantle : orifice of 
generative organs q 
Shell internal, rudimentary, thin, subspiral, sigaretiform. 
Jaw with numerous delicate ribs, as in Cylindrella. 
Lingual membrane with peculiar, long, narrow teeth, centrals bluntly tri- 
cuspid, laterals and marginals bluntly tricuspid. 
Porto Rico. 
For figure of the shell, see Genera of Recent Mollusca, Pl. LX XII. Fig. 6 a; | 
for jaw and lingual membrane, see Ann. Lyc. Nat. Hist. of N. Y., X., Pl. XL; 
for description of animal, see Shuttleworth, Bern Mit., 1854, p. 34. 
The appendiculate mantle and position of the respiratory and anal orifice 
distinguish it from Peltella, and the jaw seems different. 
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