22 MEMOIRS OF THE CARNEGIE MUSEUM. 



Plate II, fig. 2. 



Previously reported as a distinct form, only by Grier (191S) but referred to by Ortmann, 19096, 

 p. 203, as Quadrula ruhiginosa. 



Characters of variety: Much smaller than F. flava and F. flava trigona, generally 

 less than half their size and bulk. The shape of this form is much like that of the 

 var. trigona (subtrapezoidal), although sometimes there are found more triangular 

 specimens, which incline towards the western F. flava undata. With regard to the 

 swelling of the valves, there is great variety, some specimens being almost as flat 

 as the normal F. flava, but on the average, the swelling, and also the development 

 of the beaks, is more like that of F. flava trigona, with the diameter generally 

 over fifty percent of the length. Color of epidermis, when young, rather light, 

 yellowish brown (in Lake Erie), or greenish brown (in Winona Lake), with very 

 distinct and regular, dark growth-rests, and fine, indistinct greenish or brownish 

 rays. Old shells become darker, chestnut-brown or greenish blacli (the latter is 

 the case in Winona Lake). Old siaecimens are sometimes unusually drawn out at 

 the lower posterior end, and thus become oblique. 



L. H. D. Pr.ct. 



Size: 1. Erie, Cat. No. 61.3886 59 mm. 49 mm. 31 mm. .53 



2. do. Cat. No. 61.4371 . .57 " 49 " 33 " .58 



3. do. Cat. No. 61.4513 (Type set) 52 " 41 " 27 " .52 



4. do. Cat. No. 61.4370 41 " 35 " 23 " .56 



The first two shells are very old, the largest at hand, and they are much 

 drawn out posteriorly; the third and fourth are good average specimens. 



Soft parts: They have been alluded to by Ortmann (1912, p. 241), under F. 

 undata. A gravid female with young glochidia was subsequently secured from 

 Cedar Point, Ohio, and, as far as could be made out, the glochidia agree in shape 

 and size with those of F. flava. 



Breeding seaso7i: Gravid females were found in Presque Isle Ba}" on July 

 8, 9, and 12, 1910. They did not have glochidia. The specimen from Cedar 

 Point with young glochidia was collected July 24, 1911. 



Remarks: This is the Lake Erie form of F. flava, and a similar form is found in 

 Winona Lake in Indiana. The latter agrees in size, and also in general shape, 

 although the tendency toward the triangular shape of F. flava undata is more 

 pronounced. It is, however, more greenish brown in color, while specimens from 

 Lake Erie are more yellowish or rusty brown. One specimen from Winona Lake 

 is as flat as F. flava. 



The variety from Lake Erie is quite distinct, characterized chieflj^ by its 

 small, dwarfed size, and by having more distinct and regular growth-lines, a 



