40 COELOCENTRUM. 



remaining, and measures, length 37, diam. 9% mm. The in- 

 ternal column is very strongly swollen below the middle within 

 each whorl, abruptly contracted below the swelling, and is 

 sculptured with very irregularly spaced, more or less serrate 

 lamellae, which within the penultimate whorl are chiefly broken 

 into white granules. 

 Var. rufescens v. Mart. PI. 12, fig. 8. 



Smaller and more cylindrical, pale reddish-brown, the aper- 

 ture more protracted (3% mm.) and comparatively smaller. 

 Length 42 mm. ; diam. of the penultimate whorl 8, largest 

 diam. (third whorl before the last) 8^2 mm. ; preserved whorls 

 15; aperture 6 mm. long, 5 l /2 broad. Mexico, Patel coll. 

 (v. Martens}. 



This form seems to differ but slightly if at all from typical 

 clav a Pfr., though it is unlike the clava of Crosse & Fischer in 

 contour. 



Var. ATTENUATUM (Pfeiffer) . PI. 12, figs. 9, 10. 



Shell deeply rimate, swollen-turreted, rather thin, closely 

 arcuate-costulate, diaphanous, corneous. Spire attenuated 

 above, the apex entire, obtuse. Suture margined; whorls 27, 

 a little convex, the last narrower, shortly free, obsoletely 

 thread-carinate below the middle; base compressed. Aper- 

 ture a little oblique, suboval, somewhat channelled at the base ; 

 peristome continuous, whitish, narrowly reflexed, the colu- 

 mellar margin dilated, spreading. Length 41, diam. 9 mm.; 

 greatest length of aperture, inside, 4^, width 3% mm. (Pfr.). 



Chiapas, Mexico (Ghiesbreght). 



Cylindrella attenuata PFR., Malak. Blatt. iii, 1856, p. 258 ; 

 Conchyl. Cab., pi. 9, f. 1,.2; Monogr. iv, p. 698. CROSSE & 

 FISCHER, Moll. Mex., p. 404. 



The type of this species was an individual with the apex 

 entire, such as occurs rarely among normally decollate cylin- 

 drellas. I am disposed to place under attenuatum the shell 

 figured as clava by Crosse & Fischer (pi. 12, fig. 13), as well 

 as some of the specimens before me, which differ from typical 

 clav a in their greater attenuation above. One of these is pale 

 brownish, with 19 whorls remaining, and measures, length 

 39!/2, diam. 9 mm. 



