64 PLEKOCHEILUS. 



Subgeneric divisions. 



Two rather closely allied sections compose this genus : 



1. PLEKOCHEILUS s. str., in which the shell is wrinkled or mal- 

 leated, spire costulate. (Page 64). 



2. EURYTUS, shell granulate or striate, rarely almost smooth. 

 (Page 69). 



The second of these groups has an extended range southward in 

 the elevated regions of Colombia, Ecuador, Peru and Bolivia, where 

 the typical group does not extend. 



Section PLEKOCHEILUS Guilding, 1828. 



Plekocheilus GUILDING, Zoological Journal iii, p. 532 (1828), type 

 and sole species P. undiilatus=aurmileni. Pelekocheilus BECK (in 

 part) Index, p. 55. Pelecocheilus ALB., (first species only) Die 

 Hel., p. 151. Pelecycheilus MART., (exclusive of type and all but 

 last species) Die Hel. 1860, p. 188. Plecocheilus H. & A. ADS., 

 (first species only) Gen. Rec. Moll., ii, p. 147. Plecochilus AGAS., 

 Norn. Zool. Tnd. Univ., Moll. (\847).Pleocheilus M. E. GRAY, Figs. 

 Moll. Anim., pi. 74, f. 1. Caprella GUILDING, Trans. Linn. Soc. 

 London, xiv, 1825, p. 341, type C. undulata (aurissileni). Not 

 Caprella Lam., 1801. Pupa, Auricula, Carychium, Voluta and Bul- 

 sp. of some authors. 



Shell ovate or ovate-acuminate, solid, roughly sculptured with dense 

 longitudinal wrinkles broken by oblique or irregular malleation, the 

 spire longitudinally costulate; nep ionic shell small, most minutely 

 granose; aperture ovate, the lip well reflexed ; columella dilated 

 above, with a weakly convex oblique entering fold, which sometimes 

 bears a strong or slight white callus fold. Type S. aurissileni. 



Plekocheilus has been misunderstood by Martens, Pfeiffer and other 

 systematists, who restrict it to the group of B. distortus Brug. 



The group of B. speciosus, which I have left in the next section,. 

 Eurytnx, may perhaps as naturally be placed here ; but there is a 

 difference in the structure of the columellar fold. In Plekocheilus 

 this fold when strong is formed by a callus superimposed upon the 

 rather weak columellar convexity, and added only when the in- 

 dividual is quite mature. 



