﻿PLAGIOI,y\ 709 



Unio doiiacifoniiis Liv\, Tr. Am. Phil. Soc, III, 1828, p. 267, 

 pi. IV, fig. 3; Obs., I, 1834, p. 9, pi. TV. fig. 3. — Hani.ey, 

 Biv. Shells. 1843, p. 183, pi. XXII, fig. 41. — Chenu, 111. 

 Conch., 1858. pi. XI, figs. 4, 4a, 4b. 



Margarita (Unio) donaciformis Lka, Syn., 1836, p. 18; 1838, 

 ■ p. 16. 



Margaron (Unio) donacifonuis Lea, Syn.. 1852. p. 24; 1870, 



P- 3^- 

 Plagiola donaciformis Baker, Moll. Chicago. Pt. i. 1898. pi. 



XIII, fig. 4. — Simpson. Syn.. 1900. p. 605. 

 Unio rjigzag Lea, Tr. Am. Phil. Soc, III, 1829, p. 440. pi. xii, 



fig. 19: Obs., I. 1834. p. 54. pi. XII, fig. 19. — H.\NLEY, Biv. 



Shells. 1843. P- ^83, pi. XXII, fig. 42. — KusTER, Conch. Cab. 



Unio, 1852, p. 42, pi. VIII, fig. 3. — Chenu, 111. Conch., 1858, 



pi. VIII, figs. 8, 8a, d>h\ Man., 1859, II, p. 138, fig. 670.— 



Sov/ERBV, Conch. Icon., XVI, 1866. pi. xxxix, fig. 213. 

 Margarita (Unio) zigzag Lea, Syn.. 1836. p. 18: 1838, p. 16. 

 Margaron (Umo) cigcag Le.\, Syn., 1852, p. 24; 1870, p. 36. 

 Unio nen'osa Conrad, New F. W. Shells. 1834, p. 70. 

 Unio ncr-i'osus Say. Am. Conch., VI, 1834. — Kuster. Conch. 



Cab. L'nio. 1861, p. 175, pi. ia^ fig. 4. 



A beautiful and variable species, occasionally quite abundant. 

 The pattern of coloring varies greatly, there being occasional 

 shells with unbroken rays, which look like a compressed, 

 drawn-out elegaiis. Rarely the shell is a uniform ashy or dirty 

 yellowish-green as is sometimes the case with that species. It 

 is generally more inflated than F\ niocrodon, but it is quite 

 probable that it gradually merges into that species in the south- 

 west. I collected at one time in southern Kansas and Indian 

 Territory and many specimens found in that region seem to 

 stand between the two forms. A specimen before me from 

 Cincinnati. Ohio, is very much like P. macrodon. but has a 

 slightly more distinct color pattern. 



Plagioi.a macrodon (Lea). 



Shell long ovate, subcompressed. subsolid. with scarcely 

 elevated, compressed, flattened beaks, their sculpture consisting 

 of very fine doubly-looped ridges that are sharply angled at 



