BULIMUS. 127 



less confluent, transverse, irregulai- lines, and small spots ; whorls 

 about six, a little convex ; suture not profoundly impressed ; labrura 

 (in some specimens) with a thickened line or rib on the inner sub- 

 margin ; within white, with a perlaceous tinge. 



Length one and one fifth of an inch. Greatest breadth seven 

 tenths. This species appears to be not uncommon in Mexico, as 

 many specimens were sent me by Mr. Maclure ; but from what 

 particular locality, I know not. 



An original drawing of this species by Mrs. Say, under 

 which is written, in the hand of her husband, " Bulimus 

 alternatus — Mexico, Wm. Maclure,^'' is copied on plate 80, 

 fig. 3. This figure, in connection with the description, re- 

 moves all doubt as to what shell Say had before him as 

 alternatus. 



It is, however, an extremely variable shell, being found 

 on the same bush in large quantities, among which is 

 every variety of marking. Some specimens exist without 

 hardly any white in their coloring, as in the case of the 

 specimen from Buena Vista figured (pi. 80, fig. 1), while 

 some are but slightly varied with the brown vittaB. 



B. alternatus occurs in large quantities in Texas and 

 the neighboring Mexican State of Tamaulipas. Adams 

 also quotes it from Louisiana, on the authority of one 

 dead specimen found in Otter Creek, (Nat. Hist. Red Riv. 

 La. p. 254). 



Forbes, in the description of land-shells collected by the 

 Herald and Pandora, P. Z. S. 1850, p. 54, speaks of " Bui. 

 alternatus" being found at Panama. He gives no author- 

 ity for the name ; PfeifFer describes no other alternatus 

 than Say's. 



Binney was familiar with B. alternatus, as he figured it 

 on pi. li. a, and a variety of it on pi. 11. fig. 2. He con- 

 sidered it, however, a variety of B dealbatus. 



Pfeiffer alone, of foreign writers, notices B. alternatus, 

 by repeating Say's description as of a species unknown to 



