BULIMULUS-ORTHOTOMIUM . 125 



Bulimus chemnitzioides FBS., P. Z. S., 1850, p. 55, pi. ix, fig. 6. 

 PFR., MOD. Hel. Viv., iii, p. 303, 1853; Chemn., Conch. Cab., ed. 

 ii, Bulimus no. 113, pi. 31, figs. 21-23. Bulimus (Xcesiotus) chem- 

 nitzioides PFR., Malak. Blatt., p. 160, 1855. Bulimulus (Omphalo- 

 styla) chemnitzioides H. & A. ADS., Gen. Rec. Moll., ii, p. 161, 1855. 

 Bulimulus (Pleuropyr (jus) chemnitzioides MARTENS in Albers 

 Heliceeu, ed. ii, p. 221, I860. PFR., Norn. Hel. Viv., p. 254. 1881. 

 REIBISCH, Isis, 1892, p. 24, t. ii, fig. 4. STEARNS, Proc. U. S. 

 Nat. Mus., xvi, p. 381, 1893. Bulimulus (Pleuropyrgus) lima REI- 

 BISCH, Isis, 1892, p. 25, t. ii, fig. 5. Bulimulus (Xcesiotus) chemnitzi- 

 oides Fbs., BALL, Proc. A. N. S. Phila., 1896, p. 445, pi. 17, f. 4 

 (dentition). 



" The younger specimens named lima by Reibisch (pi. 24, fig. 43) 

 though apparently differing somewhat in form, appear to grade 

 directly into the others. This species sometimes shows a small but 

 distinct parietal tooth or callosity, but this is quite exceptional." 

 (Dalt). 



Buliminus lyelliae Beck, Index Moll., p. 70, from the " I. Gallap- 

 pagos," is a nude name. Beck places it between B. calvus and B. 

 jacobi. 



Subgenus ORTHOTOMIUM Crosse & Fischer, 1874. 



Orthotomium C. & F., Moll. Terr, et Fluv. Mex., i, p. 473, 1874, 

 type B. sufflatus. PILSBRY, Nautilus, ix, p. 114, 1896. DALL, 

 Proc. U. S. Nat. Mus., xix, p. 357, 1897. 



+ Globulinus C. & F., I.e., p. 475, type B. sufflatus; Hormus 

 BINNEY & TRYON, not Albers ; Peronceus, Scutalus, Thaumastus, 

 Mesembrinus of authors, not Albers. 



Shell umbilicate or rimate, varying from ovate-globose to cylin- 

 drical or pillar-shaped ; never with spiral color-markings; with the 

 initial 1* to 2 whorls sculptured with vertical riblets, the interspaces 

 often minutely striate spirally ; a decided apical dimple or pit. 



Distribution : Central and northern Mexico, southwestern U. S. 

 and Lower California. 



Distinguished from Ncesiotus and Protoglyptus by geographic dis- 

 tribution and the general aspect of the shell, rather than by any 

 definable differences. In other words, while the group is a natural 

 one, comprising specific forms of undoubtedly common ancestry, it 



