88 



mide subfusco ; dente cardinali in valva dextra elevato, trigono, 

 in v. sinistra longitudinali, compresso-triangulari ; margarita 

 purpurascente ; limbo argenteo. Long. 4 ; alt. 1J- ; lat. 1 poll. 

 Hab. Wallavvalla, Oregon ; Sacramento River, California. 



Mr. Lea and others have regarded this as a variety of A. mar- 

 garitifera ; but besides the uniformly peach-blossom nacre, the 

 form is generally more arcuate, the exterior more waved, the 

 color darker, the anterior tooth in the right valve is comparatively 

 obsolete, longitudinally oblique and lamellar in the young. 



Unio famelicus. T. parva, tenuis, transversa, oblongo- 

 ovata, convexiuscula, epidermide fusco-castaneo induta ; mar- 

 gine dorsali arcuato ; margine ventrali rectiusculo ; latere antico 

 angusto ; latere postico oblique rotundato ; umbonibus haud ele- 

 vatisad quadrantem anteriorem sitis ; dente cardinali obliquo, com- 

 presso, valido ; dente laterali brevi, recto : margaritasubpurpurea. 

 Long. 1^-: alt. £ ; lat. § poll. Hab. Wallavvalla, Oregon. 



A small and rather remarkable species, like a miniature U. 

 complanatus. It is more equilateral, has no dorsal angles, the 

 dorsal and ventral margins diverge more, and the cardinal teeth 

 are more oblique. 



Unio lutulentus. T. transversa, compressa, sub-falcata, 

 valde inequilateralis, concentrice undulato-striata interdum no- 

 dosa vel sursum rugosa, fusco-virescens ; lateribus rotundatis ; 

 marginibus sub-parallelis ; umbonibus prominulis, erosis ; denti- 

 bus cardinalibus obliquis, compressis, in valva dextra bifid is ; 

 dentibus lateralibus elongatis, compressis, rectis : margarita 

 argentata ; limbo antice incrassalo. Long. 2 ; alt. 1 ; lat. § poll. 

 Hab. New Zealand. 



Resembles U. monodon, and slender specimens of U. compla- 

 natus. It is not a fragile shell, and the peculiar tubercular waves 

 along its slope, the scattered corrugations on its disc, and its 

 peculiar color, are its best diagnostic marks. These are usually 

 concealed by a thick coat of black earth. It is said to come 

 from streams in the vicinity of chalybeate springs. 



Unio profugus. T. transversa, elongato-ovalis, ventricosa, 

 epidermide fusco-castaneo, concentrice undato-striato, radiatim 

 obsolete plicato induta; margine ventrali vix arcuato; margine 

 dorsali sub-recto ; latere antico rotundato ; latere postico oblique 



