124 University of California Publications in Geology [VOL. 8 



This form resembles L. packardi, n. sp., but it has a much less 

 height, its beak is more anterior and its length is greater. It some- 

 what resembles Malletia chehalisensis Arnold in shape. 



YOLDIA GESTEKI, n. sp. 

 Plate 7, figure 5 



Shell thin, very compressed; anterior end, the shorter, and equally 

 rounded above and below; posterior end, slightly longer, pointed; 

 posterior dorsal margin very slightly concave; escutcheon, long, nar- 

 row; base, rounded and most prominent beneath beak, from which 

 point it curves regularly to the pointed, posterior end; beaks, incon- 

 spicuous; sculpture consists of fine, rounded concentric threads. 



This species is not as convex as Y. cooperi Gabb of the Miocene, 

 its posterior dorsal margin is not as concave as that of Y. cooperi, and 

 the decoration is much finer. 



Dimensions. Length, 28 mm. ; height, 12 mm. ; convexity, 2 mm. 



Occurrence. Lake County at University of California localities 

 784 and 790. 



Named in honor of Mr. Clark Gester, Geologist, Kern Trading and 

 Oil Company. 



The outline of the shell is restored by a dotted line. 



YOLDIA(?) POWERSI, n. sp. 

 Plate 7, figure 6 



Shell small, thin, elongated, slightly curved, shaped like a pruning 

 knife. Beak, situated a fifth of the length from the anterior end, 

 prominent. Anterior end, broadly rounded; posterior end, pointed 

 sharply. Anterior dorsal margin, convex, short ; posterior dorsal edge, 

 concave, long. An impressed groove extends on the cast from the 

 beak to the posterior end parallel to and just below the posterior dorsal 

 edge. This groove divides the sharply pointed posterior end. Surface 

 marked by rounded concentric lines which do not show on the type. 



Dimensions. Length, 10 mm. ; height, 25 mm. ; convexity, 1 mm. 



Occurrence. Type specimen at University of California Locality 

 1556, lower zone, north of Mount Diablo. It is abundant at this 

 locality and appears to be characteristic of this horizon. It is easily 

 distinguished from Y. gesteri, n. sp., by its more prominent beaks, 



