368 PEOCEEDINGS OF THE MA1A.C0L0GICAL SOCIETY. 



lunate; peristome thin; columellar margin nearly perpendicular, 

 rounded, and reflected. Major diam. 5*7 mm. 



Animal. — Poot well divided ; the peripodial margin would appear 

 in life to be paler than the part above, a small overhanging lobe. 

 There is a small pointed right shell lobe, also a well-developed left 

 shell lobe (Figs. 2b, 2g). The animal was in a very hardened state ; 

 plain water had scarcely any effect in softening it, so I used at 

 last a little caustic potash. This, of course, destroyed the internal 

 organs, but I secured the radula ; the jaw unfortunately was not 

 found. This radula has the formula 60 . 2 . 10 . 1 . 10 . 2 . 60, or 

 72 . 1 . 72 ; total in row, 145. The centrals and admedians are on 

 elongate quadrate plates, the main point or mesocone being long 

 and spindle-shaped ; below the side cusp there is a conspicuous sharp 

 shoulder; the marginals are very evenly bicuspid, becoming gradually 

 very minute towards the outer edge ; some of these minute teeth are 

 tricuspid; there is no serration, as seen in the teeth of the radula 

 of Lamprocystis. 



EXPLANATION OF PLATE XY. 

 Fig. 



1, \a. Leptodontarion Perakensis, n.sp. Shell, x 4'5. 

 \b. Ditto. Cambridge specimen, Avitli animal. 



\c. Ditto. Animal, right side. Natural History Museum specimen, x 4-5. ot, 



oral tentacle. 

 \d. Ditto. Animal, left side. Ditto, x 4*5. 



2, 2a. Sltala(?) Gunon ff ensis, n.s'p. Shell. x 4-5. 



'2b. Ditto. Animal, shell removed, from right side, x 4'5. 

 2c. Ditto. Ditto, from left side, x 4-5. 



3. Helicarion permolle, Stol. From figs, in J.A.S.B., 1873, pi. i, fig. 11. 

 Enlarged and natural size. 



