422 JOURNAL OF CONCHOLOGY. 



CLAUSILIA BIDENTATA var. CRAVENENSIS. 



J. W. TAYLOR, F.L.S. 



This interesting and fine variety has long been known to 

 English conchologists under the name of var. dubia Drap., and 

 latterly has been included or confounded with the var. suttoni 

 Westl. by Dr. Boettger, Westerlund, Clessin, and others. 



The Clausilia dubia Drap. is especially distinguished from 

 C. rugosa, according to its author, by its fewer whorls and 

 smaller size, the figure he gives (pi. iv. f. lo) being only 12 mill, 

 long, and showing, as stated in the description, 9 to 10 whorls. 

 The figure indicates a stouter shell than C. rugosa, and, indeed, 

 shows much affinity in general outline to Ptipa secale. 



The true var. suttoni was originally published and described 

 in the 'Journal of Conchology' (vol. i., p. 35, Aug. 1874) as var. 

 schlechtii Zelebor, and is especially distinguished by a smooth 

 shell, resembling Clausilia laminata in its smoothness and 

 transparency, the typical specimens in ray possession possess- 

 ing II whorls, and showing no striation under an ordinary lens. 



The typical cravenensis is especially characteristic of the 

 West Yorkshire Highlands, and has a shell composed of about 

 13 whorls, and measures 17 mill, long by 3^^ broad. 



The striation obsolete in true suttoni is strongly developed 

 in cravenensis, and give the shell a distinctly reticulate appear- 

 ance. The palatal callus is also strongly developed in craven- 

 ensis, but is weak and sometimes hardly perceptible in suttoni. 

 The inferior lamella is in cravenensis distinctly and strongly 

 bifurcate, but this is indistinct in s7ittoni, and when perceptible 

 is more abruptly divaricated. The sub-columellar lamella is dis- 

 tinctly visible at the aperture in cravenensis, but not so in suttoni. 



The name bidentata is adopted for the species on the 

 authority of Dr. O. Boettger of Frankfort, the chief authority 

 upon the group, who has satisfied himself that the prior claim 

 of Strom's name is entitled to recognition. 



J.C., vii., Oct. 1894. 



