﻿DROMUS ^1-7 



long, coiled ovisacs placed in the center of the outer gills. So 

 different is this marsupium from any other known form that 

 I have been compelled to give it supergeneric rank. 

 Dromus capf;ratl's (Lea). 



Shell subelliptical. rather solid, subinflated, somewhat ine- 

 quilateral, with rather high but slightly compressed beaks, 

 which turn forward a little over a deep lunule ; posterior ridge 

 sharp above, fading out below ; surface with low, irregular, 

 concentric ridges and growth lines with one rather stronger 

 ridge on the earlier growth, and often with one or more low 

 kno'bs placed on the median line; epidermis greenish-yellow, 

 with two sets of rays rather faintly indicated, consisting of 

 bands of broken lines or dots, with narrower, alternating rays 

 made up of blotches and flecks of green; hinge plate wide; 

 left valve with two low pseudocardinals, the hinder larger, and 

 two short laterals ; rig'ht valve with three pseudocardinals, the 

 anterior and posterior ones vestigial, and one somewhat 

 blurred or bifid lateral ; beak cavities deep and compressed ; 

 muscle scars small, somewhat impressed; pallial line rather 

 distant from the border in front; nacre silvery, white, straw- 

 color, often salmon or red behind, thickened in front. 

 Length 60, height 52. diam. 25 mm. 

 Tennessee River svstem. 

 Type locality. Clinch River, Tenn. 

 Unio caperatiis Lea, Pr. Am. Phil. Soc, IV, 1845, p. 164 ; Tr. 

 Am. Phil. Soc, X, 1848, p. 75, pi. V, fig. 14; Obs., IV, 1848, 

 p. 75, pi. V, fig. i4._REf;vE, Conch. Icon., XVI, 1864, pi. v, 

 fig. 19. 

 Margaron fUnio) caperatiis Lea, Syn.. 1852, p. 22 ; 1870. p. 34. 

 DroiiiMS caperatus Simpson, Syn., 1900, p. 615. 

 Uiiio ahacoides Hai.demax, Pr. Ac. N. Sci. Phila., Ill, 1846, 

 P- 75- 



I am almost certain that this is only a variety of D. dromas, 

 but I have never been able to quite connect the two. The 

 description of this species exactly fits the other except that this 

 shell is more compressed, a little more delicate, rather less 



