Call — The Unionidce of Arkansas. 11 



Length, 53.00 mm. ; breadth, 18.50 mm. ; height, 30.00 mm. 



The synonymy of this species has been but partially worked 



out, but it is certain that it will include the following forms: 



Uaio patulus Lea. 1829. Trans. Am. Philos. Soc, Vol. 



III, p. 409, PI. XII, Fig. 20. 



Unto decisus Lea. 1830. Trans. Am. Philos. Soc, Vol. 



IV, p. 92, PL XII, Fig. 23. 



Unio chattanoogaensis Liesi. 1858. Jour. Acad. Nat. Sci. 

 Phila., 2d series, Vol. IV, 1859, p. 209, PI. XXV, Fig. 90. 



Unio consanguineus Lea. 1861. Jour. Acad. Nat. Sci. 

 Phila., 2d series, Vol. V, p. 67, PL VII, Fig. 217. 



Unio pallidofulvus Lea. 1861. Jour. Acad. Nat. Sci. 

 Phila., 2d, series, Vol. V, pp. 83-85, PL XI, Fig. 232. 



Unio intervenius Lea. 1861. Jour. Acad. Nat. Sci. Phila., 

 2d series. Vol. V, p. 84, PL XI, Fig. 233. 



Unio concolor Lea. 1861. Jour. Acad. Nat. Sci. Phila., 

 2d series. Vol. V, p. 89, PL XII, Fig. 237. 



Unio anaticulus Lea. 1861. Jour. Acad. Nat. Sci. Phila., 

 2d series, 1862, Vol. V, p. 92, PL XIII, Fig. 240. 



Unio crehriviitatus Lea. 1861. Jour. Acad. Nat. Sci. 

 Phila., Vol. VI, 1866, p. 43, PL XV, Fig. 41. 



Unio curtus Lea. 1859. Jour. Acad. Nat. Sci. Phila., 

 2d series, Vol. V, 1861, pp. 92-103, PL XVII, Fig. 253. 



Both this last named form and Uiio anaticulus were based 

 on deformed specimens of Uniones and are, in a certain sense, 

 pathologic forms. To this synonymy must be added those 

 other names under which Say described this species a leading 

 term of which will be Unio modioliformis, as had been noted 

 by the editors of Lamarck, in 1838. Other great groups of 

 Uniones there are which exhibit a far larger synonymy than 

 does that group which this species of Lamarck heads. 



So far as known this form does not occur west of the Mis- 

 sissippi, nor has any member of the group been found which 

 may be located west of that stream. It has its greatest 

 development in the mountain regions of Georgia, Alabama, 

 Kentucky, and Tennessee, though it ranges, as specimens at 

 hand prove, from western New York to Ottawa river, 

 Canada, thence west to Illinois and south to middle Alabama, 

 where some of its forms are exceedingly abundant in the 



