204 Macieay Memortat Vouvume. 
Summary.—The chief peculiarities of the mollusc under discussion are: the 
uncoiling of the whorls and the insertion of the intersutural supplementary plate of 
the shell, the partial atrophy of the mantle lobes, the numerous convolutions of the 
vas deferens and the sac developed on the penis near the origin of its retractor muscle. 
The resemblance, both external and internal, of Parmacochlea to Helicarion calls for 
its classification beside that genus in the subfamily e/carzonine, while the differences 
between them clearly entitle it to generic rank. The abnormal shell induces me to 
suppose a descent and divergence from some form very similar to le/carion robustus, 
Gould. 
EXPLANATION OF PLATE. 
PLATE XXVIII. 
Fig. 1.—Animal of Parmacochlea fischeri, as contracted by alcohol, magnified, seen from the left side, 
showing 6. left dorsal mantle-lobe. Magnified. 
Fig. 2.—The same from the right side, showing a. right dorsal mantle lobe. Magnified. 
Fig. 3.—Genital system of the same. Magnified. 
Fig. 4.—Detail sketch of penis, further enlarged, showing p. penis-sheath, 7.m. its retractor-muscle, 
x. cecum, k. flagellum, and v.d. vas deferens. 
Fig. 5.—Shell of the same, as seen from above after stripping off the mantle. Magnified. 
Fig. 6.—The same, removed and seen from within. Magnified. 
Fig. 7.—Jaw of the same. Magnified. 
Figs. 8, 9 and 10.—Teeth from the centre and margin of the radula of the same. Much magnified. 
Fig. 11.—Animal of Helicarion robustus, Gould, for comparison with the preceding, from life, viewed from 
the left side and magnified. 
