542 UNIO 
A widely distributed circummediterranean form, which, 
though somewhat variable in minor characters, 1s reasonably 
constant. Of course every possible variation has received 
specitic names and often a single form has been repeatedly 
named. It differs from U. pictorum and U. tumidus, its near- 
est allies, by being almost constantly somwhat rhomboid, the 
base line being almost straight. Usually the texture differs 
a little from that of either of those species but this difference 
is hard to describe in words. It is perhaps a little more smoky 
externally and the rest periods are usually more plainly marked. 
A careful comparison of material received since the Synopsis 
was written convinces me that the Unio ravoisieri of Deshayes 
is only a rather dark U’. turtoni, which is not so rhomboid as 
the majority of specimens of that species. 
Var. moreleti Deshayes. 
Shell Jarger than the average manifestation of U.. turtoni; 
epidermis brownish, dirty yellowish or yellow-green. 
Length &6, height 37, diam. 22 mm. 
Algiers. 
Unio moreleti DesHayes, Hist. Moll. Alg., 1848, pl. crx, figs. 
1-4; pl. cxu, fig. 5—JKoret, Icon., new ser., II, 1886, p. 4, 
pl. XcRae 226. 
Margaron (Unio) moreleti Lea, Syn. 1870, p. 60. 
? Unio maccarthyanus BourcuicNat, Moll. Nonv. Litis., 1886, 
p. 220, pl. xxxtv, figs. 8-11. 
Unio ravoisieri, (part), Simpson, Syn., 1900, p. 687. 
I have seen two lots of shells bearing the name Unio more- 
leti from the Morelet collection; one from Orleansville, Al- 
giers, is U. turtoni pure and simple, the other, a single shell 
from La Calle, Algiers, is much like Deshayes’ figure of more- 
leti and is probably a variety of turtont. 
UNIO MUSSOLIANUS Kuster. 
Shell oblong, elliptical, solid. subinflated or inflated, inequi- 
lateral; beaks full and elevated, their sculpture consisting of 
rather faint corrugated, somewhat doubly-looped ridges, but 
