NO. 1205. SYXOrSIS OF THE NAIADES-SIMPSON. 701 



UNIO CALLOSUS Lea. 



* Unio caUosus Lea, Pr. Am. Phil. Soc. II, 1841, p. 31; *Tr. Aui. Phil. Soc, VIII, 



1842, p. 239, pi. xxiii, fig. 54; * Obs., Ill, 1842, p. 77, pi. xxiii; fig. 54.— 

 * CoNiiAD, Pr, Acad. Nat. Sci. Phila., VI, 1853, p. 246.— ■ H. aud A. Adams, Gen. 

 Rec. Moll., II, 1857, p. 492.— ^Ciienu, 111. Conch., 1858, pi. xxvi, figs. 4, 4a, 

 4&.— * B. H.Wright, Check List, 1888.— "P.etel, Conch. Sam., Ill, 1890, p. 147. 



* Margaron ( Unio) caUosus Lea, Syn., 1852, p. 33; 1870, p. 33. 



Said to come from the Ohio Canal below Columbus. I am sure that 

 the locality is wrong, and it appears to be a Mexican form. The type 

 is not in the Lea collection. 



UNIO MEXICANUS Philippi. 



* Unio mexlcanusFHUAPPi, ZeLts. fiir Mai., IV, 1847, p. 95. — 'Philippi, Abbild. iind 



Beschr., Ill, 1849, p. 110, pi. xi, fig. 3.i— * Kuster, Conch. Cab. Unio, 1862, p. 

 285, pi. xcv, fig. 7. — *B. H.Wright, Check List, 1888. — -"P.etel, Conch. Sam., 

 Ill, 1890, p. 159.—* Fischer and Crosse, Miss. Sci., Pt. 7, II, 1894, p. 593. 



* Margaron ( Unio) mexicanus Lea, Syn., 1870, ]). 53. 



Mexico. 



(Group of Unio semigranosus.) 



Shell triangular rhomboid, solid, inflated, with a distinct posterior 

 ridge; beaks rather full, their sculpture consisting of numerous some- 

 what irregular corrugations which pass into the pustulous sculpture of 

 the shell; surface of the valves generally more or less sculptured with 

 chevron- shaped or zigzag ridges or corrugations, which often break into 

 pustules, the posterior slope bearing curved, radiating plications which 

 are likewise sometimes nodulous; epidermis dark, scarcely rayed ; pseu- 

 docardinals strong, radial, ragged; laterals heavy, obliquely striated; 

 beak cavities not deep, compressed; muscle scars well impressed; 

 nacre purple, with bronzy or coppery shades. 



Animal apparently not different from that of other related Unios. 

 I have not seen any with the marsupium filled. 



t UNIO PLEXUS Conrad. 



* Margarita ( Unio) carhonariiis Lea, Syn., 1836, p. 192; 1838, p. 17.2 



* Unio carhonarius Lea, Tr. Am. Phil. Soc, VI, 1838, p. 37, pi. xl, fig. 32 ; * Obs., II, 



1838, p. 37, pi. XI, fig. 32.— *TROSCHEL,Arch. fiir Naturg.,V, 1839, Pt. 2, p.236.— 

 ^Hanley, Test. Moll., 1842, p. 184; ^ Biv. Shells, 1843, p. 184, pi. xxii, fig. 

 10. — *Catlow and Eeeve, Conch. Nom., 1845, p. 57. — *Chenu, 111. Conch., 

 1858, pi. XXIII, figs. 1, la, 1&.— *P^etel, Conch. Sam., Ill, 1890, p. 147. 

 ""Margarita ( Unio) pliciferus Lea, Syn., 1836, p. 13; 1838, p. 14. 



* Unio pliciferus Lea, Tr. Am. Phil. Soc, VI, 1838, p. 61, pi. xvii, fig. 53 ; *Obs., II, 



1838, p. 61, pi. xvii, fig. 53.— "^ Tkoschel, Arch, fiir Naturg., V, 1839, Pt. 2, p. 



' A miserable figure of some rhomboidal, rather compressed form, probably group- 

 ing "with caUosus. 



2 The names carhonarius and. pliciferus were published two years before Unio plexus, 

 but were not accompanied by a description. Part X of the Mouography appeared 

 in May, 1838, and the transactions containing Dr. Lea's description of carhonarius 

 June 15, according to Scudder. Dr. Lea places his carhonarius in the synonymy of 

 pliciferus, though the former comes first in his paper. 



