BULIMULUS-ORTHOTOMIUM. 127 



a". Oblong species of Lower California, 



Group of inscendens, p. 148. 

 II. Lip expanded, surface generally granulate, 



Group of B. montezuma, p. 141. 



Group of B. alternatus. 



Thaumastus of authors, not of Albers (see Vol. x, p. 43). Rhab- 

 dotus (in part) ALBERS, Die Hel., 1850, p. 164, not Rabdota Dej., 

 1833. 



A group of few species, of which B. dealbatus and its varieties 

 and B. alternatus are excessively variable, prolific in individuals 

 and widely distributed. B. durangoanus is known by only one 

 specimen, and B. nigromontanus by several in very poor condition. 

 The latter, if less removed geographically, would from the material 

 as yet collected, be judged a variety of dealbatus ; but it lies far to 

 the west of the known range of dealbatus and alternaius, and may 

 show more distinctive features when good specimens come to light. 



The group as a whole differs from most of the Lower Californian 

 forms in lacking spiral sculpture. It closely resembles the Chilian 

 section Lissoacme (Vol. x, p. 154), but differs in apical sculpture. 



B. DURANGOANUS Martens. PL 18, figs. 32, 33. 



Shell perforate, rather lengthened, irregularly striatulate, some- 

 what shining ; white, with scattered dots and little streaks of dia- 

 phanous-gray. Whorls 6, the first and second subglobose, vertically 

 costulate, pale brownish, the following a little convex with rather 

 impressed suture, last moderately attenuated below. Aperture less 

 than half the shell's length, a little oblique, ovate, acute above ; 

 peristome simple, the outer margin straight, thin, arcuate, basal 

 margin arcuate, columellar margin dilated above and a little 

 reflexed. Alt. 15, diarn. 6; aperture, length 6J, width 4 mill. 

 (Martens). 



Villa Lerdo, State of Durango, northern Mexico (Hoge). 



Bulimulus (Peronceus') durangoanus MART., Biol. Centrali Amer- 

 icana, Moll., p. 246, pi. 16, f. 11, lla. 



A small and slender member of the group of dealbatus, ragsdalei 

 and mooreanus, with the translucent gray dots and streaks of many 

 specimens of the latter, from which its reduced size, small mouth 

 and slender figure will distinguish it. The resemblances to B. 



