295 



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 bifidis ; 

 dentibus lateralibus elongatis, compressis, rectis : margarita 

 argentata ; limbo antice rncrassato. Long. 2 ; alt. 1 ; lat. f poll. 

 Hah. New Zealand. 



Kesembles 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 plicate induta; margine ventrali vix arcuato ; margine 

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

 truncate, ad apicem obtuse ; umbonibus ante-medianis, elevatis, 

 erosis ; dentibus cardinalibus obliquis, elongatis, compressis ; 

 dentibus lateralibus remotis, sub-arcuatis : margarita livido-albida. 

 Long. 2f ; lat. ^ ; alt. U poll. Hab. Hunter's River, N. S. 

 Wales. 



Slender varieties have much the appearance of the more 

 expanded forms of U. lutulentus. It is more tumid, the beaks 

 more elevated and more central, the hinge more curved, the 

 cardinal tooth of the right valve more oblique and distinctly 

 bifid, the lateral tooth of the left valve less extensively cleft, and 

 I cannot find that it is ever nodular along the posterior slope. 



Unio verecundus. T. tenuis, inequilateralis, transversa, ova- 

 to-oblonga, convexiuscula, luteo-olivacea ; margine dorsali recto ; 

 margine ventrali arcuato ; latere antico rotundato ; latere pos- 

 tico oblique rotundato; natibus prominulis, acutis, undulatis, 

 erosis : cardo exilis ; dentibus tenuibus longitudinalibus : marga- 



