Call — The Unioniduz of Arkansas. 43 



and dorfeuillianus, all intergrading in so marked a manner 

 that identity must be regarded as established. From the 

 Little Arkansas, at Wichita, Kansas, come numbers of magni- 

 ficent examples of schoolcraftii, some entirely covered with 

 pustules, others absolutely devoid of even a semblance of one ; 

 indeed, the writer's collection contains some fifty examples 

 from that stream, exhibiting every phase of nodulation from 

 absolutely smooth specimens to those showing great numbers 

 of small pustules. The characters of the cardinal teeth 

 alone would have sufficed, in the hands of species mongers, 

 to make a dozen " extremely characteristic " species. 



The Des Moines river, in central Iowa, presents only the 

 form to which Mr. Lea gave the name of Unio schoolcraftii. 

 From this form of the shell a number of the figures given 

 have been made. As in typical j^stulosus so here there is 

 every degree of nodulation and even of rotundity of form. 

 Unio vallatus from Alabama, which was collected by the writer 

 in great numbers in Alabama a few years ago, much resembles 

 the form from Iowa even in the numbers and disposition of the 

 pustules. The female is often somewhat emarginate, but 

 does not approach Unio pustulatus Lea in that respect. In 

 refulgens the truncated posterior is the most marked differ- 

 ential feature. Plates XII to XIV represent schoolcraftii in 

 its various phases. 



Unio rectus Lamarck. 



Plate VII, (male in outline.) 



Historie Naturelle des Animaux sans Vertebres, 1819, 

 Vol. VI, p. 74; described from Lake Erie. Same, 2d 

 edition, Vol. VI, p. 537, 1838; Reeve, in Conchologia 

 Iconica, Vol. XVI, Unio Plate XIX, Fig. 86, 1865, the 

 figure is that of a large and old male; Conrad, Monograph 

 of Unio, PI. XV, 1836. 



Unio proelongus Barnes. Am. Jour, of Sci. and Arts, 

 1st series, Vol. VI, No. 1, p. 261, Fig. 11, 1823. 



Unio sageri Conrad. Monograph of Unio, 1836, p. 

 53, PI. XXIX, from the Detroit river. 



Unio leprosus Miles. Annual Report of the Geological 



