GASTEROPODA. 153 
Found at the island of Clermont Tonnere. Couthouwy. 
If this be not the young of some other species, which I somewhat 
suspect, it is very well marked by its colour alone; the contrasting 
of the white and violet, and its numerous ribs being beautifully dis- 
played. It is larger than C. egenwm. 
Figure 173, front view of the shell, enlarged; 173 a, natural size; 
173 b, details of sculpture. 
Genus PELEX.—Goutp. 
Testa parva, navicelloidea, tenuis ; vertice terminali, obliquo: apertura 
ampla, ovalis: cavositas septo angusto posticali horizontah partita ; 
septi margine ab latere sinistro disjuncto, et in processum gracilem 
contortum producto. 
This curious shell resembles a minute Navicella or Crepidula, for 
which it was for along time mistaken, until the peculiarity of the dia- 
phragm was noticed. ‘The detachment of its edge from the side of the 
shell forms a fissure or sinus, rounded at its base, directed towards the 
apex of the shell, and seems designed for the safe passage of some 
important organ. Nothing is known of the animal, except that it in- 
habits fresh water. Its affinities would seem to be with Navicella and 
Neritina, with which it is therefore associated. The new genus 
Gundlachia, of Dr. Pfeiffer, established upon a West India shell, has 
very similar characters; but the septum occupies a very much larger 
proportion of the shell, and the peculiar conformation at its left extre- 
mity does not exist or was overlooked. Our shell comes from New 
Zealand. 
PeLEX LATERALIS (Gould). 
Testa parva, crepiduloidea, tenuis, viz striata, oblique ovata, elevata , 
vertice sublaterali prominulo, acuto, incurvo ; epidermide olivaceo : 
apertura ovalis, intus olivacea ; peritremate postice expanso: septum 
album, concavum, ad trientem altitudinis situm ; margine acuto ; aculeo 
lateraliter compresso. 
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