86 THE NAUTILUS. 



pale orange or orange- brown. The eggs and placentae are 

 whitish, cream color, pale yellow, but in most cases of a pecul- 

 iar and characteristic pale orange, and also the gonads of the 

 female often have the same color. These colors agree with 

 those of P. clava, but incline more frequently to the pale orange 

 type. It should be remarked, however, that all specimens from 

 Little River, Blount Co., Tenn. (about a dozen) represent a 

 peculiar color variety. The structure of the soft parts is en- 

 tirely normal, but the color is of the orange type, and the pla- 

 centae are bright red (in over half a dozen gravid females). 

 The shells of these specimens do not at all differ from those of 

 the form argenteum, as found in Virginia, except that the color 

 markings of the epidermis are absent, and that the latter is 

 comparatively dark (brown to black-brown). However, all of 

 my specimens of this form are rather large. One of my females 

 from Chickamauga Creek had pink placentae, the others had 

 them cream color, as is normal. 



Of the typical P. oviforme (form of the rivers of medium size), 

 gravid females have been found on May 11, 13, '13; May 20, 25, 

 '14; July 5, 7, 9, 10, 13, '13. Glochidia are at hand from 

 July 5. 



The anatomy is exactly like that of P. oviforme argenteum, as 

 described above, and the glochidia have the same shape and 

 size (0.16 mm.). 



Color of the soft parts whitish, inclining on foot and mantle 

 often to yellowish-brown or pale orange. Ova and placentae 

 white, more rarely cream color or pale orange. Thus, in color, 

 this form more closely resembles P. clava. 



Of the swollen type, P. oviforme holstonense, I have found only 

 few specimens. No gravid females have been secured, but 

 sterile females and males. The anatomy is exactly as in typi- 

 ical oviforme. 



Note. Lexingtonia dolabelloides conradi, chiefly in young speci- 

 mens, often resembles the typical P. oviforme in the shell. But 

 in the color of the soft parts they are quite distinct, and the in- 

 tensely orange tints seen in the former have never been observed 

 in the latter. Gravid females of P. oviforme are recognized also 

 by the light-colored placentae, which are not quite so solid a 



