268 [ FEBRUARY, 
Sub-genera of Unio. 
Noputaria, Con. 
Shell nodose; cardinal teeth robust, single in the right valve; in each valve 
the principal cardinal tooth is parallel with the lateral teeth, or directed towards 
the posterior extremity of the shell. 
Unio Douglasie, Gray. 
Irwwea, Swains. South America. 
Shell with corrugated radiating folds on the beak or umbo; cardinal teeth 
granulated, generally curved, elongated. Third muscular impression distinct, 
not confluent, situated under the anterior portion of the cardinal tooth. 
Unio granosus, Lam. To this subgenus I would refer U. solisiana, D’Orb., 
U. Paranensis, Lea, U. rhuacoica, D’Orb., U. Fontainiana, D’Orb., U. hylea, 
D’Orb., U. Guaraniana, D’Orb., U. Matoniana, D’Orb., U. Psammoica, D’?Orb., 
U. charruana, D’Orb. ; 
This sub-genus is very distinct from any of those existing in North America, 
nor, indeed, does there appear to be any sub-genus in South America identical 
with a Northern group. 
~ Mysca, Turton. Europe. 
The type of this sub-genus, U. pictorwm, has the third anterior muscular 
pression deep, and more distinct from the large one, than occurs in any American 
species of Unio. 
im. 
Lanceouaria, Con. China. 
Shell elongated; cardinal teeth widely bifid; third muscular impression 
situated at the base of the anterior lobe of the cardinal tooth, not confluent, 
and very profoundly impressed; accessory impression small and confluent with 
the superior margin of the large impression; pallial impression slightly 
deflected anteriorly. 
U. Grayanus, Lea. 
Cauatura, Con. Africa. 
Shell thin, not elongated; beaks corrugated or subnodular; cardinal teeth 
laminar, greatly elongated, parallel with the anterior hinge margin; anterior 
accessory muscular impressions confluent with the lower part of the larger one ; 
pallial impression slightly deflected. 
U. Aegyptiacus, Caill. 
Cunicuna, Swatns. North America. 
Shell compressed, thick, lateral teeth robust and receding from the dorsal 
margin, posterior accessory muscular impression not confluent, and placed at 
the extremity of the lateral teeth. 
U. fascrolaris, lineolatus, Eastbrookianus, subtentus, celatus, arcus, &e. 
I have founded this subgenus on other characters than those given by 
Swainson. 
GuLeBuLA, Con. Lousiana. 
Shell with the cardinal teeth granulated and profoundly sulcated or divided 
into 4 or 5 lobes, irregular, diverging, somewhat resembling those of Paxyodon; 
posterior muscular impression very large and confluent with the accessory, 
which is obsolete. 
U. rotundatus, Lam. 
Uniomerus, Con. 
Shell elongated, not thick, with parallel dorsal and basal margins; beaks 
with obliquely concentric plice. | ! 
U. declivis, camptodon, subcroceus, Sayii, rivularis, perrectus, symmetricus, 
and excultus. 
The members of this group inhabit almost exclusively the small streams and 
ponds in the Southern States. 
