THE NAUTILUS. 75 



Arkansas line, and followed in general the present course of the 

 St. Francis River.* 



In the Cache River bottoms occasional forests of cypress are 

 found, though not as frequently as in the swamps east of the 

 Ridge. Generally the lowlands are so flat that, as has been well 

 remarked, " near the North boundary of Clark County it seems 

 to be a matter of indifference to many streams whether they flow 

 into the Cache or into the Black River." The ecologist will 

 find in Harper's " Phyteographical Notes on the Coastal Plain 

 of Arkansas,"! data of much value concerning the vegetation on 

 Crowley's Ridge and the adjacent Prairie regions. 



The writer collected a large number of mussels from Cache 

 River at Nemo in Craighead County, on the Bonnerville and 

 Southwestern Railroad, on June 19th, 1914. Since then col- 

 lecting has been done in Black River and also in the St. Francis. 

 Little and Tyronza rivers on the East of the Ridge, and a com- 

 parative study of the forms obtained will be shortly undertaken, 



Of the nineteen species listed from the Cache, the Quadrula, 

 which is described below, proved to be the most abundant form, 

 though Crenodonta trapezoides (Lea) and Lampsilis hydiana (Lea) 

 were very common. No univalves were found except Vivipara 

 contectoides (W. G. Binn) and Campeloma lewisii (Walker). I 

 am indebted to Dr. Bryant Walker for a revision of my identi- 

 fications. 



LIST OF SPECIES. 



Lampsilis hydiana (Lea). 



Lampsilis fallaciosa (Smith) Simpson. 



Eurynia subrostrata (Say). A peculiar form approaching 

 nasuta, but only a few females were obtained. 



Eurynia lienosa, (Con.)? A single young shell, but most 

 probably of this species. 



Carunculina parva (Barnes). 



Proptera purpurata (Lam.). 



Paraptera gracilis (Lea). 



Obovaria castanea (Lea). 



*See Branner, An. Kep. Geol. Sur. 1889, Vol. II, p. xiv. 

 tThe Plant World, February 1914, Vol. 17, pp. 36-48. 



