NO. 1205. SYNOPSIS OF THE NAIADES SIMPSON. 609 



* Unio rerrucosns SAY, Am. Conch., VI, 1834. * CONRAD, New F. W. Shells, 1834, 



p. 72. *FERUSSAC, Guer. Mag., 1835, p. 27.* CONRAD, Pr. Ac. N. Sci. Phila., 

 VI, 1853, p. 259.* KUSTER. Conch. Cab., 1862, p. 273, pi. xcn, fig. 1.* Sow- 

 ERBY, Conch. Icon., XVI, 1868, pi. I, fig. 4. 



* Tritogonia rerrucosa AGAI-SIZ, Arch. flir. Nat., I, 1852, p. 48. 



* Tritigonia verrucosa SMITH, Bull. U. S. Fish Com., 1899, p. 291, pi. LXXXI. 



t TRITOGONIA TUBERCULATA var. OBESA Simpson. 1 



Mississippi drainage generally; streams falling into the Gulf, of 

 Mexico from the Alabama system west to central Texas. 



f TRITOGONIA CONJUGANS B. H. Wright. 



* Unio conjugans B. H. WRIGHT, Naut., XIII, 1899, p. 89. 



* Tritogonia conjugans Simpson, Pr. Ac. N. Sci. Phila., 1900, p. 79, pi. iv, tig. 1. 



Hiawassee River, Tennessee. A single male shell of this remarkable 

 species, the type, is in the TJ. S. National Museum collection. I am not 

 positive that it belongs here, though it probably does. 



MESOGENvE. 



Male and female shells alike, short, solid, inflated; embryos occupying 

 a few distinct ovisacs in the center of the outer gills. 



Genus CYPROGENIA Agassiz, 1852. 



(Type, Cnio irroratus Lea.) 

 Cyprogenia AGASSIZ, Arch, flir Nat., 1852, p. 47. 



Shell solid, inflated, rounded triangular, sometimes slightly retuse, 

 generally a little biangular behind; posterior ridge unusually well 

 developed, especially in the young shell; umbonal region flattened 

 parallel with the axis of the shell, sometimes compressed ; beaks curved 

 inward and forward, their sculpture very faint, consisting of slightly 

 doubly looped ridges; sculpture of the shell nodular, radiately wrinkled, 

 or lachrymose; ligament black and conspicuous; luuule distinct and 

 well developed; epidermis shining, painted with a delicate, dark mot- 

 tling on a light ground; hinge plate wide and flat; pseudocardiuals 

 heavy, triangular, blunt and ragged; laterals short, obliquely striated; 

 cavity of the beaks not deep; adductor scars small, well impressed, 

 those at the posterior round; nacre bright and silvery. Animal with 

 inner gills partly free from the abdominal sac, rounded below; outer 

 gills smaller; marsupium consisting of from seven to twenty-three very 

 long, purple ovisacs pendent from near the central base of the outer 

 gills, and formed into a close coil with the ends turned inwardly; bran- 

 chial opening large with many small papilla; anal opening smooth. 



1 A short, inflated, peculiarly formed shell from Big Eddy, Nechez River, Texas, 

 having very few faint tubercles is in the U. S. National Museum collection, and may 

 be a distinct species. It is certainly worthy of the varietal name here applied, 

 Proc. N. M. vol. xxii 39 



