ORTMANN: monograph of the naiades of PENNSYLVANIA. 75 



Localities represented in the Carnegie Museum: 



Ohio-drainage: 

 Allegheny River, Godfrey, Armstrong Co., Pennsylvania. 

 Ohio River, Cooks Ferry, Beaver Co., Pennsylvania. 



Tennessee-drainage: 



Tennessee River, Florence, Lauderdale Co., Alabama (H. H. Smith); Bridgeport, Jackson Co., Alabama 



(B. Walker, donor). 

 French Broad River, Boyd Creek, Sevier Co., Tennessee. 



Holston River, Mascot, Knox Co.; Hodges, Jefferson Co.; Holston Station, Grainger Co., Tennessee: 

 Clinch River, Sol way, Knox Co.; Edgemoor and Clinton, Anderson Co., Tennessee. . 



Distribution (See fig. 8): Type locality, Ohio River (Rafinesque). 



Wherever found, in Pennsylvania, as well as in the Tennessee-drainage, this 

 form is associated with the main form, and does not show any remarkable facts 

 in its distribution. 



Pleurobema obliquum catillus (Conrad) (1836). 

 Quadrula solida (Lea) Simpson, 1914, p. 885; Pleurobema obliquum catillus (Con- 

 rad) and Pleurobema catillus (Conrad) Utterback, 1916, p. 79, 82. 



Plate VI, fig. 6; Plate VII, fig. 2. 



No records from Pennsylvania previous to those given below. 



Characters of variety: This form may be briefly characterized as a P. obliquum, 

 in which the radial furrow is obliterated. In all other respects it resembles the 

 main species, and varies in the same way. The shell is more or less subtriangular, 

 upright or somewhat oblique. The diameter is always considerable, fifty percent 

 or more of the length. The nacre is generally white, rarely pinkish. 



L- H. D. Pr.ct. 



Size: 1. Industry, Cat. No. 61.3895 83 mm. 65 mm. 48 mm. .58 



2. Industry, Cat. No. 61.3895 81 " 69 " 45 " .56 



3. Godfrey, Cat. No. 61.4567 61.5 " 51 " 32 



.0 



9 



Soft parts: Identical with those of the main form, and also the glochidia. 



Breeding season: Gravid females were found on May 22, 1914; June 22, 1909; 

 June 24, 1909. Glochidia on June 24. Specimens from the White River in Ar- 

 kansas were gravid, containing eggs on August 2 and 5, 1914. 



Remarks: This form likewise is not sharply separated from the main species, 

 and is connected with it by very gradual transitions, but it has a better claim to be 

 recognized as a variety than var. cordatum, since it seems to replace the main species 

 at least in certain regions. It has been largely misunderstood by previous authors, 



