Clark and GilletU — Ifnionida of Little Arkansas Hirer. 67 



Compared with the species as generally known, these shells exhibit the 

 same departures from the general type as those exhibited by the Q. pus- 

 tulosa just mentioned; that is, they are unusually compressed, and note- 

 worthy for the fewness and smallness of pustules which are frequently 

 altogether absent on the posterior ridge. The sulcus is also unusually 

 shallow. The shells, however, average larger than in ordinary collections. 

 The nacre is white and clear, and free from stains. 



Q. lachrymosa is a very fair commercial species, and the specimens 

 from the Little Arkansas are considerably superior to the ordinary type 

 on account of the flatness and smoothness of the shell. 



:;. Symphynota complanata (Karnes). 

 HEELSPLITTER. 



Fifteen examples of this species were obtained, ll' from near Wichita, 

 and :; from Valley ( !enter. 



The heelsplitter dwells in a variety of situations such as ponds, sloughs 

 and the more quiet portion of rivers. It varies considerably in minor 

 details such as thickness of shell, development of wing, etc., but is gener- 

 ally pretty uniform in general shape. Bayou-dwelling examples are 

 usually roughened, thin-shelled and badly stained, so that they have no 

 commercial value. In some places (the upper Mississippi) the shells are 

 peculiarly truncate posteriorly, as if they had abruptly stopped growing 

 in that part of the shell. 



We have had no opportunity to study the bodies of S. complanata from 

 Little River. < Jenerally speaking the species is, like the Anodontas, quite 

 markedly subject to the attack of parasites, leeches being occasional, Atax 

 frequent and Aspidogaster concliicola abundant. River-dwelling mussels 

 are usually not so badly affected as those living in sloughs, and from these 

 perfectly formed and excellent shells it would appear that parasites are 

 not especially abundant here. 



Symphynota complanata is usually too thin, and sometimes too badly 

 Stained to be of any value in the manufacture of buttons so that it is not 

 generally regarded as a commercial species. On account of its flatness 

 and broad expanse of shell, when it develops a sufficient thickness of 

 shell it is an excellent button species. No other native freshwater shell 

 except the immense thick (Jandrula linos and the beautiful but valueless 

 Anodonta suborbiculata equals it in surface, and where it can be w^'d 

 more buttons can be cut from a ton of shells of this species than from any 

 Other freshwater mussel. 



The specimens from the Little Arkansas are exceptionally fine. We 

 have seen none to approach them in excellence except a few examples 

 much like them collected in Perche Creek, Missouri, by Doctors Lefevre 

 and Curtis, of the University of Missouri. Some of the shells, both from 

 Perche Creek and Wichita, are unusually elongate, and all are remarkably 

 smooth and heavy. The nacre is of a clear soft satiny texture, pearly 

 white in all but '2 examples, in which it is a very faint warm yellowish 

 pink, too faint to be more than a mere suggestion of color and very 



