376 



NORTH AMERICAN INDEX FOSSILS. 



and by obscure radiating ridges most prominent anteriorly, 

 markings are preserved also on molds. 

 Abundant in Knoxville of California. 



These 



II. Clinopistha Meek. 

 Moderately convex, with nearly straight basal margin, rounded 

 posterior, and short, subnasute anterior end. Callosity present in 

 place of lunule, anterior to beaks. Surface marked by fine growth 

 striae. Hinge possibly crenulated. Ligament external. Pallial 

 line simple. Devonic and Carbonic. 



3. C. subnasuta (Hall & Whitfield). (Fig. 477, b-c) Devonic. 

 Hinge line gently arcuate. Anterior end nasute. 



Hamilton : Kentucky. 



4. C. radiata Hall. (Fig. 478, b-c.) Carbonic. 

 Anterior end scarcely nasute. 



Coal Measures : Ohio-Missouri. 



III. Phthonia Hall. 

 Elliptical, with short anterior end. Beaks small and appressed. 

 Hinge line straight or slightly arched. Umbonal slope more or 

 less distinctly defined. Surface marked with fine concentric striae, 

 and at times with radiating striae. Ligament external. Pallial 

 line simple. Devonic. 



P. cylindrica Hall. (Fig. 477, d.) Devonic. 



5- 



Radiating striae obscure or absent. Hinge arched. 

 Hamilton : New York. 



IV. Sanguinolites McCoy. 

 Equivalve, elongate, obliquely truncate behind, with beaks low 

 and near the anterior end. Surface concentrically striated and 



Fig. 479. Sanguinolites ceolus. (Pal. Ohio, II.) 



bearing a ridge extending from the beak to the basal posterior 

 margin. Teeth absent; anterior adductor scar buttressed by a 

 ridge. Ligament external. Pallial line simple. Miss. -Carbonic. 



