234 UNIO 
ually a little higher in front than behind and subangular or 
very slightly produced on the base line just back of the middle 
of the shell. 
Hanley says of this species [Ipse Linnzei Conchylia, p. 27] : 
“More uniones than one are present in the | Linnean] collec- 
tion, but upon the whole the U. pictorwm of authors | Rossm. 
Icon., fig. 196] agrees best with synonymy and description. 
The figure referred to of Lister is U. pictorum; Bonanni’s 
drawing is more doubtful and was possibly meant for U. tumi- 
dus. The descriptions in Fauna Suecica and Systeme are 
brief and unsatisfactory and might suit either species alike.” 
Var. /ongirostris Rossmassler. 
Shell greatly elongated, olive, brown, or dirty yellowish- 
green. 
Length 70, height 28 mm. 
Unio longirostris RossMASSLER, Icon., III, 1836, p. 26, pl. 
Xiv, fig: 200; X11, 1842, p. 13¢pl, rv, fist 738: 
Unio pictorum (part), SIMPSON, Syn., 1900, p. 682. 
This form may possibly be worthy of varietal rank. It 
seems to be smaller than the ordinary manifestation of the 
species, is more elongated and duller colored and lacks rays. 
UNIO PLATYRHYNCHUS Rossmassler. 
Shell elongated, subinflated, inequilateral, rather thin to sub- 
solid, dorsal and ventral lines parallel, anterior end subtruncat- 
ed, pointed above; posterior end compressed and curved down- 
ward into a decided beak, which usually extends below the 
base line; beaks full, slightly elevated, their sculpture consist- 
ing of corrugated ridges, which break up into nodules, which 
are strongly developed on the posterior ridge; posterior ridge 
rounded ; surface with irregular growth lines; epidermis finely 
folded along the growth lines, generally smooth on the middle 
of the disk, rough behind, dirty greenish to burnt-brown;; left 
valve with two greatly compressed pseudocardinals, which are 
sometimes united, and two delicate, straight, lamellar laterals, 
