1916] 



Packard: Mesozoic and Cenozoic Mactrinae 



307 



MULINIA DENSATA Conrad var. MINOR Arnold 



Mulinia densata, var. minor Arnold, U. S. Geol. Surv. Bull. 396, p. 54, 

 pi. 5, fig. 6, 1909. 



This variety is characterized by its smaller size, and its more 

 inequilateral form than the typical M. densata. Its hinge is un- 

 known. 



The type of this variety was obtained from Jasper Creek, Fresno 

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

 Museum under catalogue number 1 6.1601. The dimensions as meas- 

 ured on the original figure are : length, 42 mm., height, 36 mm. 



Occurrence. — Pliocene: Etchgoin (Arnold). Miocene: Vaqueros 

 (Arnold). 



MULINIA ALTA (Weaver) 



Pseudooardium gabbi (Remond) var. altuvi Weaver, Wash. State Geol. 

 Surv., Bull. 15, p. 68, pi. 7, fig. 69, 1912. 



P. gabbi, var. elongatum Weaver, op. cit., p. 68, pi. 10, fig. 78. 

 P. gabbi, var. robustum Weaver, op. cit., p. 69, pi. 7, fig. 68. 



This variety was described by Weaver as follows : 



This variety is large, somewhat compressed; beaks moderately high but 

 not especially prominent for the genus. Anterior and posterior margins 

 have steep slopes, the latter being more pronounced. The altitude is much 

 greater in proportion to the longitude than in the case of the other varieties. 

 The dimensions of the type are: length, 75 mm., height, 78 mm., con- 

 vexity, 30 mm. 



The type specimens of Pseudocardium gabbii var. crttum, P. gabbi 

 var. elongatum and P. gabbii var. robustum were kindly loaned the 

 writer by Dr. C. E. Weaver of the University of Washington. 



The hinges of these three type specimens have been exposed and 

 their relationships may now be definitely stated. A comparison 

 with typical specimens of Mulinia densata from California show 

 that, although the general shape of these Washington forms falls 

 within the range of the variation of the typical species, the dental 

 armature possesses differences of at least varietal value. 



The shapes of the three forms are somewhat different, but the 

 hinges are nearly identical, varying only as one individual varies 

 from another. The three specimens show the left cardinals, two of 

 them show the anterior lateral but in none of them is the posterior 

 lateral preserved. 



