THE NAUTILUS. 123 



and in nearly every mussel bed of the river; Old River. At 

 Cove Creek station in Hot Springs County, specimens were 

 collected from the Ouachita River with the cuneiform blotching 

 wonderfully developed. 



Quadrula metaaerva (Raf, ). Ouachita River, Arkadelphia 

 and Skillern's Shoals. Not found in Old River. Very com- 

 mon. The variety v:ardii was nowhere located in this region. 



Quadrula. asrpera (Lea). Old River; Terra Noire Creek at Mt. 

 Zion. 



Quadrula larhrymosa (Lea). Ouachita River at Skillern's 

 Shoals and below Arkadelphia. " A comparatively small com- 

 pressed form with large tubercles, quite different from the 

 typical form." Dr. Walker in letter to the author. 



Qv.adrula pustulosa (Lea). Ouachita River, Arkadelphia and 

 Skillern's Shoals; Caddo River; Terra Noire Creek west of Arka- 

 delphia; Old River. The shells from the last named locality 

 are very perfect. Their brilliant color and handsome appear- 

 ance make them easily the most attractive of all the "Oua- 

 chita" shells. Some excellent pearls have been obtained from 

 this species. Dr. Walker distinguishes three "forms" among 

 the Old River shells, as follows: 



a. Very oblique, usually densely pustulate. 



b. Quadrate, with a silky, polished epidermis. 



c. Intermediate. Shaped more like "b," but in epidermis 

 and sculpture like "a." He thinks that several local races of 

 this species are perhaps worthy of recognition. 



Fusconaia rubiginosa (Lea). Big Deceiper Creek, Gum 

 Springs, south of Arkadelphia. Two males from this locality 

 were stated by Dr. Ortmann to be indistinguishable in shape 

 from the Pennsylvania specimens, but they had a lighter and 

 more glossy epidermis. Some specimens collected in the Terra 

 Noire Creek, west of Arkadelphia, on July 3, 1911, are more 

 compressed than cerina, chunii, or undata. Dr. Ortmann says, 

 ^^ Rubiginosa is the small creek form — in Pennsylvania, passing 

 into a more swollen form (trigona) in the rivers of medium size, 

 and finally, in large rivers, into the true undata, with high 

 beaks. The anatomy of all the forms named (including chuini, 

 and cerina) is absolutely identical.^^ A form perfectly intergrading 



