156 CAEBONlFEilOUS PERIOD. 



Class GASTEROPODA. 



Subclass PROSOPOCEPHALA. 



Oeder SOLENOCONCHA. 



Family DENTALIID^. 



Genus DENTALIUM Linnreus, 1740. 



Dentalium canna Wliite. 



Plate XII, fig. 6 a and 6. 



Dentalium canna White, 1874, Exp. & Surv. west 100th Merid., Prelim. Rep. luvert. 



Foss., 23. 



Shell large, straight, or very slightly curved ; transverse section circu- 

 lar or nearly so; test thin; surface marked by numerous, somewhat distinct, 

 encircling lines of growth, crossed by fine, obscure, longitudinal striae, the 

 latter seen only upon well-preserved examples. Our specimens indicate 

 that some individuals of the species reached a length of ten or twelve cen- 

 timeters. The largest fragment measures a little more than nine millimeters 

 in diameter at the base, and, at a distance of five and a half centimeters 

 toward the apex, the diameter is six millimeters. 



This species is distinguished for its large size in connection with the 

 presence of encircling and longitudinal striae. It resembles D. priscum 

 Muenster fe'om the Carboniferous rocks of Belgium, as described and fig- 

 ured by de Koninck in Animaux fossiles du terraine de la Belgique, but 

 its apical angle is smaller, and the aperture is little if any oblique, Avhile in 

 that species the obliquity of the aperture is a distinguishing character. 



Position and locality. — Strata of the Carboniferous period: near Salt 

 Lake, New Mexico ; and near Relief Spring, Arizona. 



