540 I'lUH'EElHyuS <>!' THE XATIONAL MUM I'M. 



tLAMPSILIS LIGAMENTINUS var. GIBBUS Simpson. 1 

 *Unio crassus SOWKRBY, Conch. Icon., XVI, 1868, pi. xcv, fig. 520. 



Mississippi River drainage generally; southern Michigan; western 

 New York; Manitoba; Ontario; the variety from the Ohio River 

 southward. 



tLAMPSILIS ORBICULATUS Hildreth. 



* Unio orbiculatus HILDKETU, Am. Jl. Sci., XIV, 1828, p. 284. *HANLKY,Test. Moll., 



1842, p. 192; Biv. Shells, 1843, p. 192, pi. xxi, fig. 2. *CATLOW ami KEKVE, 

 Conch. Norn., 1845, p. 62. *CONRAD, Pr. Ac. N. Sci., Phila., VI, 1853, p. 254. 

 *H. and A. ADAMS, Gen. Rec. Moll., II, 1857, p. 494. *KUSTER, Conch. Cab., 

 1861, p. 216, pi. LXXI, figs. 3, 4. * SOWERBY, Conch. Icon., XVI, 1866, pi. 

 XLIV, fig. 239. *CALKINS, Pr. Ottawa Ac. Sci., 1874, p. 44. *B. H. WRIGHT, 

 Check List, 1888. * P.ETEL, Conch. Sain., Ill, 1890, p. 162. 



* Margarita ( Unio) orbiculatus LKA, Syn., 1836, p. 25; 1838, p. 19. 

 *Margaron ( Unio) orbiculatus LEA, Syn., 1852, p. 28; 1870, p. 43. 



* Unio abruptus SAY, Am. Conch., No. II, 1831, pi. xvn. *CONRAI>, New F. W. 



Shells, 1834, p. (57. *CHKNU, Bib. Couch., 1st ser., Ill, 1845, p. 24, pi. vi, figs. 

 1, la, Ib. *DESHAYES, An. sans Vert., 2d ed., VI, 1335, p. 555;* 3d ed., II, 

 1839, p. 674. 



* Unio cyclips FERUSSAC, Guer. Mag., 1835, p. 28. 



* Unio crassus CONRAD, Monog., IV, 1836, p. 34, pi. x vi. 



Ohio and Cumberland rivers; west to the Mississippi River; north 

 to Minnesota. Some specimens can hardly be separated from L. 

 higfjinsii. 



tLAMPSILIS HIGGINSII Lea.- 



* Unio higginsii LEA, Pr. Ac, N. Sci. Phila., IX, 1857, p. 84; * Jl. Ac. N. Sci. Phila,, 



V, 1862, p. 188, pi. xxiv, fig. 258; *Obs., IX, 1863, p. 10, pi. xxiv, fig. 258. 

 * SOWERBY, Conch. Icon.. XVI, 1868, pi. LXXXII, fig. 431. *B. H. WRIGHT, 

 Check List, 1888. * P^ETEL, Conch. Sam., Ill, 1890, p. 155. 



* Margaron (Unio) higginsii LEA, Syn., '870, p. 41. 



Ohio River, west to Iowa, and southwest to Kansas. 



tLAMPSILIS PINGUIS Lea. 1 



Unio'pinguis LKA, Pr. Ac. N. Sci. Phila., I, 1857, p. 84; *J1. Ac. N. Sci. Phila., IV, 

 1858, p. 78, pi. xv, fig. 58; *Obs., VI, 1858, p. 78, pi. xv, fig. 58. B. H. 

 WRIGHT, Check List, 1888. 



* Margaron ( Unio) pinguls LEA, Syu., 1870, p. 44. 



St. Peters River, Minnesota. Doubtful. 



'A peculiarly humped form of ligamentinui, common throughout the, southern 

 range of the species, may bear the above name. 



2 A somewhat puzzling species, of which male specimens often approach closely to 

 Obovaria ellipsis in form, but the pseudo cardinals are always stumpy and never longi- 

 tudinal, as they generally are in that genus. It is probably an aberrant form, 

 closely related to L. orbiculatus. The females are more inflated in the postbasal region 

 than in any other member of the group. 



3 I have seen only one specimen of this, the type, which in an exceedingly puzzling 

 form. The hinge line is injured and curves in strongly in front of the beaks, where 

 there is a large, irregular liimile. and the pscudoeardiuuls are compressed. It may 

 be a young, diseased orbiculatua. 



