210 HALIOTINELLA, GYMNOTOPLAX. 



H. MONTROUZIERI Souverbie. PI. 71, figs. 66, 67. 



Shell umbilicated, ovate-oblong, testacella-shaped, very thin, fra- 

 gile, much depressed ; apex flat, subsinistral ; white, pellucid, cov- 

 ered by a thin straw-colored epidermis. Whorls 4, separated by a 

 depressed suture, rapidly increasing, the earlier 3 rounded, last very 

 ample, planulate, forming nearly the whole shell, concentrically 

 subplicate-striate. Aperture elongate-oval, very large, shining 

 within, the margins separated ; right margin acute, left margin ar- 

 cuate, incurved toward the right, channelled outside above, vault- 

 ingly reflexed over the small umbilicus at the insertion, and con- 

 nected with right margin by a callus. Length 14, width 7, alt. 2J 

 mill. Aperture 13 mill, long, 5 wide. (Souv.~). 



Island of Art, New Caledonia (Montrouzier). 



Haliotinella montrouzieri Souv., Journ. de Conchy 1., 1875, p. 33, 

 pi. 4, f. 1. Cf. Morch, J. de C., 1876, p. 374. 



H. PATINARIA Guppy. PI. 72, figs. 75, 76. 



Shell lengthened-auriform, flat, subtranslucent, rather thin, con- 

 centrically striated, whitish ; spire very short. Whorls 4, the ear- 

 lier 3 forming the spire, last whorl very ample. Aperture long- 

 ovate, the margins separated, righf margin somewhat incurved, 

 flexuous, left margin prominent, acute, grooved outside above at 

 the umbilical fissure. (Guppy). 



St. Christopher (St. Kitts}, West Indies. 



Haliotinella patinaria GUPPY, Journal de Conch., 1876, p. 163; 

 Journ. de Conch., 1878, p. 322, pi. 10, f. 1. Compare Morch, J. de 

 C., 1876, p. 374. 



Morch considers this the shell of Pleurobranchus quadridens. 

 Genus GYMNOTOPLAX Pilsbry, 1896. 



Similar, so far as known, to Pleurobranchus, but the mantle is 

 partly open or perforate above, exposing part of the shell. This 

 condition occurs in no other Pleurobranchidce. 



G. AMERICANUS Verrill. PL 74, fig. 91. 



In alcohol the body is oblong, higher than wide, with the mantle 

 extending over the greater part of the shell. The foot is large, 

 thick, with short, rounded, grooved auricles in front, its lateral sur- 

 faces, like those of the mantle, covered with small projecting spicules. 

 Head bluntly rounded, with two broad, leaf-like oral tentacles and 



