110 THE NAUTILUS. 



05 CERTAIN IMMATURE AHCULOSS. 



BY BRYANT WALKER. 



Ancitlosa prarosa was described by Say in 1824 from specimens 

 collected at the falls of the Ohio. In the following year he de- 

 scribed a second species from the north fork of the Holston River in 

 Virginia as A. subglobosa. 



In 1838 Dr. Lea described a very small bicarinate species from 

 Cincinnati as A. cincinnatiensis, and, in 1845, another species from 

 " Tennessee and Tuscaloosa, Ala.," as A. tintinnabulum. 



Tryon in his preliminary " Synonymy of the Strepomatidae " 

 (1865) stated that cincinnatiensis was " undoubtedly the quite young 

 of prarosa," and placed tintinnabulum as a variety under subglobosa. 

 He considered A. virgata Lea, a small, smooth, rounded form, to be 

 the young of tintinnabulum and A, globula Lea, a very similar but 

 more globose shell, the immature form of subglobosa. 



In 1871, Dr. James Lewis published a paper in the American 

 Journal of Conchology (VI, p. 216) on the shells of the Holston 

 River, in which he identified a small bicarinate form from that river 

 as A. cincinnatiensis, and, by a series of specimens graded in size, 

 satisfied himself that this form was the young of Lea's tintinnabulum. 



He further states that " some of the varieties (so-called) of An- 

 culosa prarosa have bicarinate young, but their forms are such that 

 when the dimensions of Mr. Lea's typical cincinnatiensis (diameter 

 .16 inch) they do not exactly, but only approximately, correspond 

 thereto, and therefore must yield to the claims of titinnabulum." 

 Dr. Lewis did not specify the peculiar characteristics of the young 

 of A. prarosa, as distinguished from the young of tintinnabulum, 

 beyond stating that the species is extremely variable and that " in 

 one variety carina? are scarcely discernible in the smallest specimens. 

 In others there are traces of carinae upon shells of nearly or quite \ 

 inch in diameter." 



In regard to A. subglobosa he described the young as " smooth, 

 shining, depressed, subglobose, with a somewhat pointed, elevated 

 apex," and states that in his numerous series of that species " none 

 are carinate, nor can I find any evidence by which I might identify 

 subglobosa with tintinnabulum." 



His conclusion therefore was that Lea's cincinnatiensis was the 



