228 GJEOTIS. 



tentacles as usual ; mantle partially covering the shell, having an 

 appendage posteriorly on the right side. 



Shell sigaretiform, fragile and pellucid, composed of about* 2^ 

 whorls, the spire flat and near the right side, the apical whorl smooth. 

 Lower surface completely open, the margin of the ]ast whorl mem- 

 branous, not calcified, the columella a spiral lamina along the suture. 



Jaw long and low, composed of numerous narrow plaits, as in Dry- 

 mceus, Amphibulima, etc. 



Radula with the transverse rows of teeth arranged en chevron; 

 centrals with long and narrow basal plate, and a gouge-shaped, tri- 

 lobed cusp, situated far back on the basal plate. Side teeth similar, 

 but larger; somewhat asymmetrical, the median cusp of the trilobed 

 gouge much smaller than the side cusps. 



The shell of Gceotis is like that of Peltella and Cryptostrah on ; the 

 jaw is similar to that of Peltella, Amphibulima and Drymceus ; but 

 the radula has peculiar teeth, with some resemblance to those of the 

 Ortltalicince and Folyntita, and as in those genera, correlated with 

 arboreal habits. The marginal teeth of Amphibidima, and especially 

 of the subgenera Pellicula and Rhodoiiyx, are considerably like the 

 teeth of Gceotis, and show its close relationship with those groups. 



The character of the radula peremptorily forbids a union of Gceotis 

 with Peltella or Cryptostrakon. While there can be little doubt that 

 it is allied to Peltella, Pellicula, Amphibulima and Simpulopsis, espec- 

 ially the subgenus Platysuccinea, the exact relationships of these 

 genera remain unknown, awaiting a comparison of their soft anatomy. 



GcEntis lives on the trunks and leaves of trees, especially bananas. 

 It is doubtless a vegetable eater. The species now known are all 

 from Porto Rico. 



Shuttleworth has adopted the plan of measuring the altitude ob- 

 liquely, as when the shell is placed concave side down on a flat sur- 

 face. This is more properly called the convexity. I have followed 

 his method, as the altitude cannot readily or certainly be measured 

 in the ordinary way. 



The soft parts will doubtless give more satisfactory specific char- 

 acters than the shells, though the species described so far are not 

 difficult to distinguish. None of them have been figured hitherto. The 

 radula and jaw are known by Mr. W. G. Binney's researches, but 

 nothing is known of the rest of the anatomy. 



Gceotis douvillei de Morgan (Bull. Soc. Zool. de France, x, p. 388, 



