140 PROCEEDINGS OF THE ACADEMY OF [March, 
a tooth, on the columella. Shells of this exact form and coloringfoccur 
at Laredo, Webb county, on the Rio Grande (pl. VII, fig. 28). 
In a general way, the eastern (typical) form of marie from Frio 
county and Laredo eastward differs from the western (Val Verde 
county) form in several respects: 
Southeastern Form. Western Form. 
Smaller, more oblong; lip more Larger, more conic; lip less thick- 
thickened; columella frequent- ened within; no columellar 
ly toothed; often with ragged 
streaks, at least on the earlier 
whorls. Pl. VII, lower three 
lines of figures. 
tooth; often streaked, but with- 
out ragged or mottled streaks. 
Pl. VII, upper two lines of 
figures. 
We do not think it advisable at present to make a subspecific separa- 
tion, especially since none of the names proposed apply to the western 
race. The genitalia of this race are figured (fig. A). 
While almost every colony of the eastern race has slight peculiarities 
in shape, relative abundance or absence of the several color-forms, etc., 
yet with large series the intergradation is seen to be so complete that 
we can find no ground for dividing them into several races, as Prof. 
Cockerell proposes. His plan (Journal de Conchyliologie, 1891, pp. 23, . 
24) is as follows: 
1. With gray or brownish markings: 
a. Without a columellar tooth, 
b. Columellar tooth present, . 
2. Without color markings: 
a. With no columellar tooth, . . . . . . albidus Taylor. 
b. A columellar tooth, . binneyanus Pfr. MS. W. G. B. [=in- 
termedius Singl., Ckll., Corpus Christi.] 
alternatus Say. 
marie Alb. 
The true B. alternatus (type in coll. A. N. 8.) has not been found 
north of the Rio Grande, and in all probability does not reach our 
limits. The name binneyanus is preoccupied, so that were the race 
valid, we should use for that form the name intermedius Singley MS. 
Ckll., based on Corpus Christi shells. The type locality of albidus 
Taylor MS. Ckll. is Derby, Frio county, Texas. 
Many perfectly adult Corpus Christi shells have no columellar tooth, 
and hence we should have to divide them between intermedius and 
albidus. Similarly, various specimens selected from the Derby, Frio 
county, series before me would be either alternatus, albidus or inter- 
medius; while from the Hidalgo series, all four of the supposed varieties 
