recent shells. 19] 
We have three different ones here, perhaps unio sinuata, 
radiata and nanca ; but it is almost impossible to decide 
without figures, or very elaborate descriptions, neither of 
which are to be had; could either be met with, the species 
of this intricate genus might perhaps be decided upon with 
some degree of certainty. Swainson asserts, in his ‘‘ Zao- 
logical Illustrations” that the species cannot be fixed without 
both. 
Unio sinuata, ‘‘ shell ovate, oblong, compressed, sinuous ; 
on the upper part thick, cardinal tooth lobed, and striated.” 
Inhabits the Island of Orieans, not very common, I have 
sometimes found very small pearls in this species ; it is a 
coarse large mother of pearl shell with a brown epidermis. 
Unio radiata, ‘‘shell obovate, convex,rather depressed, thin, 
transversely striated, broader on the anterior side than on the 
other ; epidermis yellow, longitudinally rayed.” 
Found onthe beach at the Island of Orleans; the shell is 
much thicker than those from Saratoga, and is pink or flesh 
colour within. 
Unio nanca, ‘‘shell transversely oblong, beaks depressed, 
Jateral ; tooth deeply canaliculated.” 
This species, much more common than feither of the fore- 
going is likewise an inhabitant of the Island of Orleans ; the 
sheil is violet or clay colour within, and is rarely rayed, it is 
much lengthened the transverse way, and covered with a 
black or dark brown epidermis, under which is mother of 
pearl. 
SECOND ORDER, UNIMUSCULOSA, 
Myvetacga, Seconp Famity, 
Two of these are common in the salt water of this river, 
Modiola, 
Shell subtrahsverse, equivalve, regular, posterior side vory 
short, beaks almost Jateral, depressed on the short side.— 
Hinge without teeth, lateral, linear ; legament cardinal, al- 
y most 
