154 GEOLOGY AND PALyEONTOLOGY. 



EXOGYRA FIMBRIATA. 



Plate VII, Figure 2, a, h. 



Exogijra fimhriata, Conrad, Proc. Acad. Nat. Sci., vol. VII, p. 269. 



Upper valve very thick^ very convex, with 10 or 12 distant, concentric, prominent, imbricated 

 laminae ; surface of valve covered witli minute, semi-granular, interrupted, rugose lines ; inner 

 surface minutely subgranular interiorly ; apes nearly terminal ; lower valve unkown. 



Locality — Western Texas. 



EXOGYRA L^VIUSCULA. 



Plate VII, Figure 4, a, b. 

 Exogyra Iceviiiscula, Roemer, Kreid. von Texas, p. 70, pi. IX, fig. 3. 



Ovate, gibbous ; larger valve inflated, subliemispberical, obtusely cayinated in the middle, 

 smooth, irregularly ornamented towards the margin, with a few larger lines of increment ; umbo 

 distinctly spiral ; interior margin of the valve suborbicular, thin. 



Locality — Leon Springs. 



EXOGYRA MATHERONIANA. 



Plate VIII, Fig. 1, a, h; and Plate XI, Fig. 1, a, b. 



Exogyra Matheroniana, D'Orbigny, Palteon. Fran., vol. Ill, p. 717, pi. 485, fig. 1. 



Exogyra ])licala, (loldfuss, (not Lam.) 



Exogyra Texana, Eoemer, Kreid. von Texas, p. 69, pi. X, fig. 1. 



Exogyra Texana, Shumard, Palason. of Red river, p. 205, pi. V, figs. 1 and b. 



Obliquely ovate, convex, thick ; larger valve carinate-angulate ; ribs radiating, unequal and 

 granulate-nodose ; umbo exhibiting a point of attachment ; smaller valve granulose, with radi- 

 ating ribs, often thickened ; inner margin finely striated ; muscular impression semi-circular or 

 ovate, submedial. 



Locality — Between El Paso and Frontera. 



EXOGYRA COSTATA, var. 



Plate VIII, Figure 2. 



Exogyra ponder osa, Roemer, Kreid. von Texas, p. 71, pi. IX, fig. 2. 



Large, thick, ovate, inflated, concentrically lamellose-striate ; larger valve gibbous, obtusely 



carinated, concentric, lamella3, irregular, imbricated, laciniate towards the margin ; umbo spiral, 



free ; smaller valve thick, concentrically laminated, within smooth ; umbo distinctly spiral, 



horizontal. 



EXOGYRA COSTATA. 



. Plate IX, Fig. 1 and 2 ; Plate X, Fig. 1 ; and Plate VIII, Fig. 3. 



Exogyra costata, Say. Jour. Acad. Nat. Sci., vol. II, p. 43. Morton, Synopsis, p. 55, pi. VI, 

 fig. 1 and 4. 



Suboval, thick ; lower valve convex, costated, concentrically corrugated; costa3 somewhat 



