203 



This is a very handsome little species and quite distinct from any 

 known to me from American strata. 



Red River Bluffs, Fannin County. According to Dr. G. G. Shu- 

 mard it is very abundant in the Septariaa beds of the Marly Clay 

 Group. 



Genus Ne^ra, Gray. 



N. AL^FOKMis, (n. sp.) Shell somewhat wing-shaped, or elongate- 

 subovate ; anterior side short, strongly rounded ; umbonial region very 

 gibbous ; anterior slope falling abruptly to the margin, flattened con- 

 vex; posterior side much elongated, suddenly contracted and 

 pointed ? ; posterior cardinal margin straight or slightly sinuate ; 

 beaks elevated, incurved, acute, situated a little posterior to the 

 widest part of the shell and directed slightly backwards; pallial 

 sinus short, obtusely rounded above ; surface marked with irregular 

 fine stride of growth. 



Length, 0.94 inch ; width, 0.58 ; thickness about, 0.38. 



Resembles N. ventricosa and N. Moreauensis, Meek and Hayden, 

 {Proc. Acad. N. ScL Phil. vol. viii. p. 83), but is a much larger 

 species, and the pallial sinus is not triangidar as in N. ventricosa. It 

 may be also compared with N. caudata, Koch and Dunker, sp. 

 (Verst. Deutsch. OolitJigehild, p. 31, pi. 2, fig. 7), from which it differs 

 chiefly in its greater size. 



Bluffs of Red River, Fannin County, 



Dr. G. G. Shumard collector. 



Genus Avicula, Klein. 



A. IRIDESCENS, (n. sp.) Shell (cast) large, approaching subcir- 

 cular, very inequivalve, as wide as long; gibbous, cardinal margin 

 equal to the whole length of the shell, straight except at posterior 

 extremity, which is elevated; buccal, pallial, and anal margins 

 rounded, and together describing about three fourths of a circle ; 

 anterior wing produced, short, triangular ; right valve more gibbous 

 than the left, greatest convexity between the middle and beak ; beak 

 moderately elevated above the cardinal margin, located between the 

 middle and front ; left valve regularly rounded, most convex near 

 the middle ; muscular scars numerous, indicated in the cast by a 

 series of small granules and impressions, commencing at the cardinal 

 margin in front of the beaks, and passing in a curve downwards and 

 backwards. 



A portion of the nacre adheres in several of the casts in the State 

 Cabinet, retaining still the original beautiful iridescent hues. We 

 have not been so fortunate as to find any specimens exhibiting sur- 

 face characters. 



Length, 2.64 inches; thickness, 1.48. 



Clearly related to A. Pedernalis, Roemer, (Kreid. Texas, p. 61, 



