1917] Nomland: Fauna of the Santa Margarita Beds 305 



are found sandstones and conglomerates of Lower Etchegoin age con- 

 taining among other species several varieties of Astrodapsis arnoldi 

 Pack. 



Description of Species 

 AMIANTIS COMMUNIS, n. sp. 

 Plate 14, figures 2a, 2b, 2c, 2d 

 Type specimen, no. 11311, in Univ. Calif. Coll. Invert. Pal., from locality 

 2276, on hill near SW corner of SE % of NE % sec. 10, T. 19 S, E. 15 E, 

 M. D. B. & M. 



Shell large, rather thick, inequilateral, equivalve ; umbones promi- 

 nent, incurved, a little more than one-third of length of shell from 

 anterior extremity. Anterior dorsal margin short, concave ; posterior 

 dorsal margin long, gently convex ; ventral margin evenly arcuate ; 

 anterior end strongly curved ; posterior extremity angulated. Lunule 

 large and deep; escutcheon rather wide, extending nearly to posterior 

 end, more strongly depressed on right than on left valve. Surface 

 ornamented by numerops lines corresponding to stages of growth. 

 Left valve with three cardinals and a lateral ; anterior cardinal thin, 

 close to middle cardinal. Right valve with bifid posterior cardinal. 

 Nymph plates of both valves long and narrow. Dimensions : Height, 

 75 mm. ; length, 82 mm. ; thickness, 41 mm. 



Pitaria diabloensis (Anderson) which also occurs in the Miocene 

 of this region is somewhat similar in outline to this species, but may 

 be distinguished from it by the long, narrow escutcheon, the smaller 

 and shorter cardinal of the left valve, and the anterior and middle 

 cardinals are nearer together. 



Occurrence. — At localities 2276, 2278, northeast of Coalinga, 

 Santa Margarita. At the type locality this species occurs with Chione 

 semiplicata, n. sp. ; Periploma clarki, n. sp. ; Septifer margaritana, 

 n. sp ; Acanthina noma, n. sp. ; Tegirta thca, n. sp ; Tegula varistriata, 

 n. sp. 



CHIONE SEMIPLICATA, n. sp. 

 Plate 15, figures 2a, 21, 2c 

 Type in Univ. Calif. Coll. Invert. Palae., a nearly perfect specimen of left 

 valve, no. 11318, from locality 2283, in small gully near SE corner of NW % 

 of NW % sec. 15, T. 19 S, R. 15 E, M. D. B. & M., about nine miles northeast of 

 Coalinga. 



Shell subquadrangular to triagonal in outline; beaks prominent 

 and strongly curved inwards, about one-fourth of length of shell 

 from anterior end ; interior margins faintly crenulate ; anterior end 



