NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 765 



t PLEUROBEMA CICATRICOSA Say. 



* Unio varicosus Lea, Tr. Am. Phil. Soc, IV, 1829, p. 90, pi. xl, flg. 20; ' * Obs., I, 



1834, p. 100, pi. XI, fig. 20.—* Hanley, Test. Moll., 1842, p. 181 ; * Biv. Shells, 

 1843, p. 181, pi. XXI, fig. 14-.— *Catlaw and Reeve, Conch. Nom., 1845, p. 65.— 

 *H. and A. Adams, Gen. Rec. Moll., II, 1857, p. 496.— *Chenu, 111. Conch., 

 1858, pi. XI, figs. 6, 6a, 66.— *B. H. Wright, Check List, 1888. 



* Margarita ( Unio) varicosus Lea, Syn., 1836, p. 17; 1838, p. 16. 

 * Margaron (Unio) varicosus Lea, Syn., 1852, p. 23; 1870, p. 34. 



"Unio cicatricosus Say, N. Harmony Diss., II, No. 19, 1829, p. 292 — * Say, Am. 

 Conch., VI, 1834.—* Ferussac, Guer. Mag., 1835, p. 28.—* L. W. Say, Terr, 

 and Fluv. Shells, 1840, p. 5.—* Conrad, Pr. Ac. N. Sci. Phila., VI, 1853, p. 

 246.— *KusTER, Conch. Cab. Unio, 1861, p. 185, pi. LViii, fig. 2.—* Reeve, 

 Conch. Icon., XVI, 1864, pi. viii, fig. 31; xiii, fig. 50.— *B. H. Wright 

 Check List, 1888.— * P^tel, Conch. Sam., Ill, 1890, p. 148. 



*Unio cicatricosus var. varicosus P^etel, Conch. Sam., Ill, 1890, p. 148. 



Ohio River; Tennessee; Claiborne, Alabama. The last locality I con- 

 sider doubtful. Lea gives St. Paul, Minnesota, as a habitat, but I do 

 not think it possibly can be. 



The following species are described by Raflnesque, but I am unable 

 to make them out. 



'* Pleurohema mytiloides Rafinesque, Ann. Gen. Sci. Brux., V, 1820, p. 313, pi. 



LXXXII, figs. 8-10. 

 * Pleurohema cuneata Rafinesque, Ann. Gen. Sci. Brux., V, 1820, p. 313. 



TETRAGENE^^. 



Male and female shells alike, solid; beak sculpture consisting of 

 coaise, subparallel ridges; beak cavities deep; marsupium filling all 

 four gills, smooth, pad-like. 



Genus QUADRULA (Rafinesque, 1820) Agassiz. 

 (Type, Quadrula nietanevra Rafinesque.) 



Quadrula Rafinesque, Ann. Gen. Sci. Phys. Brux., 1820, p. 305. 

 Botundaria Agassiz, Arch, fiir Naturg, 1852, p. 48. 

 Orthonymus Agassiz, Arch, fiir Naturg, 1852, p. 48. 



Shell triangular, quadrate or rhomboid, solid, inflated, with rather 

 prominent beaks, which are generally sculptured with a few coarse, 

 irregular, subparallel ridges that are inflated where they cross the 

 posterior ridge; posterior ridge ordinarily well developed; base often 

 incurved in old specimens; disks sculptured or smooth; epidermis 

 usually dull colored, dark and rayless, or feebly rayed; hinge plate 



' I change Lea's name because Lamarck previously applied the name Unio varicosa 

 to what is, no doubt, Alasmidonta marginata. Mr. T. G. Lea, of Cincinnati, took 

 many specimens of this species, the shells of which he sent to Dr. Lea, and in several 

 of them he has written in pencil "not charged" or "ov^aries charged," with the 

 date, but neither of them seems to have described the animal. I am somewhat at a 

 loss to know where to place this curious form. The young are much like those of 

 Quadrula solida, and do not. show the swellings until the third or fourth year, and 

 occasionally the adult shell is nearly smooth. 



