382 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Jaw as in Macroceramus, described below. 



The dentition of the genus is very peculiar and constant in the various 

 groups or subgenera. The lingual membrane is exceedingly long and narrow. 

 The base of attachment of the centrals is small, long, narrow, with the upper 

 margin broadly reflected into a blunt, rounded, and expanded, gouge-shaped 

 cutting point ; the laterals have a long, subquadrangular base of attachment, 

 bearing, below, a large, bluntly rounded, greatly expanded, palmate cusp and 

 cutting point, representing the inner and central cusps of the laterals ; and, 

 above, a long, slender, graceful extension, representing the external cusp of the 

 other Helicidce. This last is bluntly truncated, or bears a recurved cusp smaller 

 but of same shape as that below ; or it has a laterally extended, small blunt 

 point. In some species the laterals extend to the margin of the lingual mem- 

 brane ; in others there are distinct marginal teeth, long, narrow, laminar, with 

 bluntly recurved apices. A full description and figures of these various forms 

 of teeth will be found in Journal de Conchyliologie, January, 1870. 



SUBGENUS GONGYLOSTOMA, ALBERS. 



Animal small and short compared with the shell, in general like that of 

 Patula; eye-peduncles of medium length, the tentacles quite short. Motions 

 sluggish ; the shell drags horizontally, nearly in the line of motion. 



Shell cylindrically fusiform or conic-turreted, apex attenuated, costellately 

 striate ; whorls 9 - 20, the last more or less protracted, terete, sometimes obso- 

 letely angulated ; aperture circular, peristome expanded in every part. 



The lingual membrane of three species only is known : C. elegans, C. ornata, 

 and C. Poeyana. They all agree in their characters. On the laterals the inner 

 cutting palmate cusp (it can hardly be called a cutting edge or point) is sur- 

 mounted by a simple, long, squarely truncated extension; the outer palmate 

 cusp is on a long pedicle; the change from lateral to marginal teeth is very 

 gradual ; the last become very small, wider than high, with one inner, large, 

 and one outer, small palmate cusp ; the two pedicles are quite wanting. 



Cylindrella Poeyana, D'ORBIGNY. 

 Vol. III. PI. LXIX. Fig. 2. 



Shell very long, thin, horn-colored or whitish, longitudinally strongly striated ; 

 spire very long, inflated, acuminate behind, truncated; whorls 11, rather con- 

 vex, the last carinated before ; aperture round ; peristome acute and continu- 

 ous, in contact with the preceding whorl. Axis simple. Length, 15 mill.; 

 breadth, 4 mill. 



Pupa Poeyana, D'ORBIGNY, Moll. Cuba, I. 185, PI. XII. Figs. 24 - 26. 

 Cylindrella Poeyana, PFEIFFER, Mon. Hel. Viv., II. 380. CHEMNITZ, ed. 2, 20, 



PL III. Figs. 29-31. W. G. BINNEY, T. M., IV. 149 ; L. & Fr.-W. Sh., I. 



22 (1869). 



