STANTON.] 



ANATINIDJE. 117 



broad, approximate, projecting considerably beyond the hinge line and 

 situated about one-fifth the total length of the shell behind the anterior 

 end. Surface marked by 25 to 28 narrow, angular, radiating cost»3, some 

 of which occasionally bifurcate. The interspaces are not quite equal, 

 even on the middle portions of the valve, and they become much broader 

 toward the anterior and posterior ends. 



Length, 46 ram ; height, 29 mm ; convexity of a single valve, about 10 mm . 

 Broken specimens in the collection show that the species sometimes 

 reached dimensions one-half greater than those given. 



This species seems to be closely related to P. breiveri Gabb, from the 

 Cretaceous of California, and it is also quite similar to P. subventricosa 

 M. & H., from the Fox Hills beds at the mouth of Judith river. From 

 the former it differs in the more elongate form, more contracted poste- 

 rior end, and less regular costae. 



Pholadomya subventricosa is known only by a single distorted speci- 

 men, but it seems to be more ventricose, and the posterior end is broader 

 and the beaks are nearer the anterior end than in our species. 



Locality and position. — Williams creek, Huerfano county, Colorado, 

 in the Pugnellus sandstone. 



ANATINID^E. 



Genus ANATINA Lamarck. 



Anatina lineata n. sp. 



PI. xxvi, Figs. 3 and 4. 



Shell of medium size, transversely subelliptical or elongate ovate in 

 outline, inequilateral ; anterior end produced, broadly aud regularly 

 rounded; posterior end short, gaping, abruptly contracted, and more 

 narrowly rounded; dorsal margin concave immediately behind the 

 beaks and gently convex in front; basal margin forming a broad curve; 

 beaks small, approximate, fissured, with an oblique internal rib behind 

 the fissure. The valves are slightly flattened in the middle, so that the 

 greatest convexity is in advance of that region. Surface marked by 

 strong concentric undulations that become obsolete on the posterior 

 third of the shell, and by more numerous fine concentric lines covering 

 the whole valve. The best preserved impression of the surface shows 

 also two to three faint radiating lines on the umbonal region. 



Length of a large specimen (anterior portion restored from other ex* 

 amples), about 70 mm ; height, 44 ,r,m ; convexity of both valves united 

 16 ,m ". 



Anatina sulcatina Shumard ? as figured by Whiteaves l and by White 2 , 

 is very closely related to the form here described. Our species has 

 somewhat more prominent beaks and it lacks the well-defined furrow 

 that extends from the beak to the base in A. sulcatina. 



i Mesozoic Fossils, vol. i, PI. 17, Pig. 5. * Bull. U. S. Geol. Sur. No. 51, PI. 6, Pig. 1. 



