20 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vol. 50 



This species, by its smooth surface, is strongly contrasted with the 

 others and is easily discriminated. The substance of the shell is soft 

 and chalky, the enamel yellowish. Two precisely similar and rather 

 well preserved specimens were obtained. 



Genus VOLUTODERMA Gabb 

 VOLUTODERMA TEXANA Conrad 



(Figure 9) 



Rostcllitcs texano Conrad, in Emory's Report on the 

 Mexican Boundary, p. 158, pi. xiv, fig. 2, 1855. 



Volutilithes navarroensis Shumard, Proc. Bost. Soc. 

 Nat. History, vin, p. 192, 1861. 



By platting the dimensions and filling in the 

 details given in Shumard's very full descrip- 

 tion, it is easy to make a diagrammatic figure 

 which is recognizable. Conrad's species was 

 figured from an internal cast, preserving only 

 a narrow strip of the outer surface near the 

 pillar. The spiral cords were taken to be 

 columellar plaits, which gave a wholly errone- 

 ous idea of this portion of the fossil. Only 

 three plaits are present. Conrad's type is pre- 

 served in the U. S. Nat. Museum (No. 9886). 

 There is no reasonable doubt that his species 

 is identical with that of Dr. Shumard, having 

 been collected from the same horizon and re- 

 gion and agreeing essentially. Since Shu- 

 Fjg. 9 — V. texana mard's species was never figured and the figure 

 Conrad, dorsal view given by Conrad represents only the internal 

 showing form and ex- cast> j t seemec j advisable to figure the better- 

 terior sculpture. 2 ,. , r . . , , . , , 



preserved form which later researches have 



brought to light and which retains the substance of the shell. Figure 

 9 represents such a specimen, No. 20,992 U. S. Nat. Museum, from 

 Kaufman, Texas. The following data, additional to those given 

 by Conrad, are deducible from the material brought together by 

 Dr. Stanton from various places in Texas, especially near Webber- 

 ville, Texas, No. 21,183. 



Pillar with three feeble plaits, becoming obsolete near the aper- 

 ture, the "numerous plaits" of Conrad being based on remnants of 



