1916] 



Packard: Mesozoic unci Cenozoic Mactrinae 



303 



end shorter and narrower than the posterior, which is evenly rounded; 

 area in front of beaks depressed concavely as a whole, but slightly elevated 

 at margin, this condition when the two valves are together, suggesting a 

 large lunule with a slightly raised ridge running down the middle; pos- 

 terior margin becomes more and more arcuate as extremity is approached, 

 sculpture consisting of numerous fine incremental lines, some of which are 

 more prominent than the great majority, these more prominent ones giving 

 a slightly irregular surface to the shell. Hinge and interior unknown, 

 but probably quite similar to S. JiempMllii. The dimensions of the type 

 are given as: length, 120 mm., height, 85 mm., convexity, 28.5 mm. 



This species was found associated with S. catilliformis var. alca- 

 trazensis Arnold. Specimens of this species have not been available 

 for study, therefore its subgeneric relationships cannot be stated. 



The type of this species was obtained from the Fernando forma- 

 tion from the Alcatraz asphalt mine, near Sisquoc, Santa Barbara 

 County, California. It was deposited in the United States National 

 Museum under catalogue number 165292. 



Occurrence. — Pliocene: Fernando formation (Arnold). 



SPISULA TEJONENSIS, n. sp. 

 Plate 27, figure 5 



Shell small, elongate, equivalve and nearly equilateral; umbones 

 not prominent, adjacent ; anterior dorsal edge slightly concave imme- 

 diately under the beaks, but then becoming straighter until the 

 rather arcuate anterior extremity is reached ; posterior dorsal edge 

 slightly convex ; posterior extremity a little more rounded than the 

 anterior ; base broadly and evenly rounded ; dorsal area limited by 

 an indistinct umbonal ridge, extending from the beaks to the pos- 

 terior extremity of the shell ; this posterior dorsal area is marked 

 by fine regularly disposed concentric ridges, which do not typically 

 extend beyond the slightly carinated umbonal ridge. Interior un- 

 known. The dimensions of the type are: length, 22.5 mm., height, 

 16.5 mm., convexity, 6 mm. 



It was with some hesitation that this form was described without 

 first studying the hinge. Its distinctive shape and its frequent oc- 

 currence in the California Eocene appear to justify the naming of 

 this form. 



This species is distinguished from 8. merriami by its less ventri- 

 cose and more elongate shape, together with its less pronounced con- 

 centric sculpture. 



The type of this species was obtained at University of California 



