Descriptions of New Genera and Species of I^ossils. 23 



with a faint, scarcely perccptii^jle nmboiial ridge, anterior to which 

 theic is a broad, very shallow and undefined depression, crossing the 

 valves from the beaks toward the basal line, and becoming obsolete 

 before reaching it. Internal markings not preserved in the specimens 

 examined. 



Sui'face of the valves marked b\' tine concentric stri;e, and by some 

 stronger undulations. 



This sliell is allied to Orthodesma parallelum. Hall, but that 

 species has the anterior end more contracted, the shell proportionally 

 longer, and the cardinal and 1)asal margins are straight for a greater 

 •listance than in 0. svbovale. 



Formation and locality: the spcciniens were found by me in the 

 Hudson River Group, at Morrow, O. 



Genus Tellinojiva, (Hall). 

 Tellixomya cingulata, n. sp. (Plate VII., figs. 19, 19o.) 



CEty. —Cinyulata, encircled with lines.) 



Shell of medium size, nearly circular, with a slight prolongation of the 

 posterior end, thus giving a little obliquit}' to the shell; anterior and 

 basal borders regularly- rounded; posterior cardinal margin slightly 

 rounded and sloping to point of greatest extension; beaks small, ob- 

 tusely pointed, and not incurved; A^alves moderately convex, somewhat^ 

 <lepressed just posterior to the beaks, and along the cardinal margin. 



Hinge plate wide, regularly, and rather strongly- arched, occupied by 

 eight to ten teeth on each side of the middle, those at the extremities 

 bent to about a right angle, becoming more and more straight toward 

 the center. 



Surface ornamented by from six to eight ver3' fine concentric lines. 



Muscular impressions and pallial line not observed. 



Length, 0.72 inch; height, 0.G8 inch; convexity, 0.22 inch. 



This species is related to 7\ pectunculoides, Hall, but its more 

 circular form, less prolonged posterior border,] the fine concentric stria' 

 and its larger size, will serve to distinguish them externalh, while its 

 smaller number of teeth, wider hinge-plate, and more abrupt curvature 

 of the same, will separate them internally. 



Formation and locality- : in the upper part of the Hudson River Gr. 

 nt Marble Hill, near Madison, Ind. Tlie type specimens were found 

 by Mr. H. Nettleroth, of Louisville, Kv. 



