140 PROCEEDINGS OF THE ACADEMY OF [March. 



a tooth, on the columella. Shells of this exact form and coloring^occur 

 at Laredo, Webb county, on the Rio Grande (pi. VII, fig. 28). 



In a general way, the eastern (typical) form of marice 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 tooth ; of ten streaked , but with- 

 streaks, at least on the earlier out ragged or mottled streaks. 

 whorls. PI. VII, lower three PI. VII, upper two lines of 

 lines of figures. figures. 



We do not think it advisable at present to make a subspecifie 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, 

 CockereU proposes. His plan {Journal de Conchyliologie, 1891, pp. 23, 

 24) is as follows : 



1, With gray or brownish markings: 



a. Without a columellar tooth, alternatus Say. 



b. Columellar tooth present, marice Alb. 



2, Without color markings : 



a. With no columellar tooth, alhidus Taylor, 



6. A columellar tooth, . . hinneyanus Pfr. MS. W. G. B. [ = in- 

 termedius Singh, Ckll., Corpus Christi.] 



The true B. alternatus (type in coll. A. N. S.) has not been found 

 north of the Rio Grande, and in aU probability does not reach our 

 limits. The name hinneyanus is preoccupied, so that were the race 

 valid, we should use for that form the name intermedius SingleyMS. 

 CkU., based on Corpus Christi shells. The type locality of alhidus 

 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 

 alhidus. Similarly, various specimens selected from the Derby, Frio 

 county, series before me would be either alternatus, alhidus or inter- 

 medius; while from the Hidalgo series, all four of the supposed varieties 



