66 Clark and Gillette — Unionidse of Little Arkansas River. 



was picked up in a rubbish pile. It was bleached and very 

 brittle, and gave evidence of having been carried a long distance. 

 It had mi doubt been washed into the river from one of its 

 tributaries. 



List of Species. 

 1. Quadrula pustulosa (Lea). 



WARTYBACK. 

 There arc 15 examples of this species, L2 from near Wichita and ."> from 

 Valley Center. These are all rather small or medium-sized shells and 

 quite uniform in character, being markedly compressed and unusually 

 smooth, most of them being entirely free from elevations and the most 

 pustulous one containing a few very low, hardly perceptible nodules near 

 the ventral border. The whole collection presented a considerable differ- 

 ence from Q. pustulosa as usually seen, and it was only after some con- 

 sideration and comparison that they were identified as this species. They 

 represent the form originally described as a distinct species under the 

 name Unio sehoolcraftii. This flat, smooth form is of occasional 

 occurrence in collections, and examples are now and then found mixed 

 in with beds of the more common inflated pustulous form. This is our 

 first experience in finding it the predominant form. The existence of 

 this and intergrading forms, along with other aberrant and peculiar 

 types, has long made (J. pustulosa a puzzling species. The history of the 

 studj of this species would be merely an account of the various attempts 

 to assemble a motley but well-connected series of forms, and authorities 

 differ somewhat as to the number of forms to include. Baker* speaks of 

 baving before him at one time 19differen1 varieties of Q. pustulosa from a 

 number of States, and Calif discusses its variability and synonymy at consid- 

 erable length, and says: " From the Little Arkansas, at Wichita, Kansas, 

 come numbers of magnificent examples of sehoolcraftii, some entirely 

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

 indeed the w liter's collection contains some fifty exam pies from that stream, 

 exhibiting every phase of nodulation from absolutely smooth specimens 

 to those showing o;reat 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." 



In view of this statement it is rather remarkable that all our specimens 

 should he so uniform. These smooth flattened shells are even superior to 

 the inflated pustulous forms for commercial purposes. All our specimens, 

 however, are of rather small size. 



2. Quadrula lachrymosa (Lea). 



MAPLELEAF. 



Of this species there are 22 from near Wichita in the collection and 10 

 from near Valley Center. They are all of large size and very uniform in 

 general appearance. 



* Mollusca <>! the Chicago Area; Bull. Ill, part 1. Nat. Hist. Survey, Chicago Acad. 

 fThe Unionidse of Arkansas; Trans. Acad. Sci. St. Louis, Vol. VII, Xo. 1, p. 43. 



