27 



rior truncation to the posterior extremity of the hinge line — the 

 meeting of the curved lower and straight upper margin giving 

 a sub-nasute extremity. Umboncs prominent, very full and 

 rounded, tho beaks closely incurved, the apices minute. Sur- 

 face marked by concentric ridges, of growth parallel to the 

 margin of the shell. 



This species has some resemblance to T. ventrico8a y in its 

 form and general outline; but it is much broader in proportion 

 to the length, less attenuate posteriorly, the beaks are nearest 

 to the anterior, and the basal margin is destitute of the sinus 

 which exists in that species, 



Length nearly seventh-eights of an inch, hight three-fourths 

 of an inch. 



Geological Formation and Locality. In limestone of the age 

 of the Trenton limestone ; at Mineral Point, Wisconsin. 



TELLINOMYA alta, (n. s.) 



Description. Shell small, sub-triangular, with rounded basal 

 margin ; valves depressed-convex. The anterior and posterior 

 portions of the hinge line are nearly straight from between the 

 beaks to beyond the muscular impression, and stand nearly aft 

 right angles to each other. The distance from the beaks to the 

 base of the shell is usually equal or nearly equal to the length. 



The muscular impressions are large and moderately distinct; 

 the posterior one elevated on the dorsal side with a broad, low 

 ridge (depression on the cast) passing from near the beak to 

 the scar. The hinge plate is marked by from twenty to twen- 

 ty-five very small carved teeth on the posterior side, and from 

 ten to fifteen on the anterior side. 



This species differs from T. astartceformis, (Ctenodoniaf 

 astartoseformis, Salter, Canadian Organic Remains, Decade I, 

 page 27,) in the more erect beaks and in the different form of 

 the posterior basal margin. 



Geological Formation and Locality. In limestone of the age 

 of the Trenton limestone; Dodgeville, Wisconsin. T. J. EaU 



TELLINOMYA VENTRICOSA, (n. s.) 



Description* Shell sub-rhomboidal, extremely ventricose, with 

 strong incurved beaks, the anterior dorsal and ventral margins 

 sub-parallel, the posterior and obliquely truncate, the anterior 

 end broadly rounded, and continuing into the basal margin; 

 posterior umbonal slope somewhat angular, with a slight sulcus 

 just anterior to it, which passes from near the beak of the 

 base. Surface marked by obscure concentric striae of growth- 



