144 PLECTOPYLIS. 



ured with spiral lines, hirsute in the young. Aperture half-round 

 or lunate, oblique, the lip reflexed, its ends generally joined by an 

 elevated parietal callus, which usually bears an entering lamella. 

 Interior of the last whorl obstructed by a barrier composed of a trans- 

 verse plate or plates on the parietal wall, and several transverse or 

 longitudinal denticles or plates on the outer wall. Type P. aehatina 

 Gray, pi. 40, figs. 5, 6, 7, 8. (See also pi. 40, figs' 1-4, P. jovia. 

 PL 40, figs. 9-12, P. ponsonbyi. PI. 40, figs. 13-15, P. fultoni). 



Foot short, rarely equalling in length the diameter of the shell ; 

 tentacles very short ; eye pedicles of moderate length. Mantle edge 

 thin, with small right and left body-lappets. Pulmonary cavity 

 small. Kidney large, triangular. 



Jaw very thin, horny, arched, with a small anterior median pro- 

 jection ; it is marked transversely with a great number of more or 

 less distant grooves which divaricate in the center (pi. 42, fig. 3(>. P. 

 cyclaspis). Radula of moderate width, long, composed of about 100 

 transverse more or less V-shaped rows of 60-70 teeth. Central tooth 

 smaller, sometimes much smaller, than the laterals, very narrow, the 

 reflection small, with three slender cusps. Lateral teeth with a large 

 inner cusp and simple or bifid outer cusp, and a minute inner cusp 

 (pi. 42, fig. 35, P. cyclaspis central, 1st, 2d and 12th laterals, and 

 20th and 25th marginal teeth. In P. pinacis the central tooth is 

 larger and more similar to the laterals. 



Genital system (pi. 42, fig. 34, P. cyclaspis) having the duct of the 

 spermatheca long. An organ of unknown hornology (either a dart 

 sack, a diverticulum of the spermatheca, or an appendicula) enters 

 the vagina just above the opening of the spermatheca duct. Uterus 

 containing few large eggs. Penis simple, receiving the vas deferens 

 and the penis retractor at its apex, the latter attached distally to the 

 floor of the lung cavity. 



This group differs from Gorilla in having perpendicular internal 

 lamellae upon the parietal wall of the shell. It is different from Cor- 

 illa and all other Helices in the converging V like elements of the 

 thin jaw, which is quite of the goniognathous type found in Cylin- 

 drella, Orthalicus and Otostomus. The small size of the central 

 teeth is also an anomalous feature, recalling the Achatinidce. Per- 

 haps the accessory organ of the vagina (seen between the uterus and 

 the spermatheca in pi. 42, fig. 34) is really a diverticulum of the 

 spermatheca duct ; and if this is the case the genital organs will not 

 differ very much from those of Gorilla, although in that genus the 



