1856.] S13 



one or two longitudinal obsolete lines ; disk finely wrinkled concentrically ; 

 upper valve flattened, deeply depressed towards the apex ; ribs rather narrower 

 than those of the opposite valve, obscurely bicarinated above, disk orna- 

 mented with close, fine, squamose, concentric wrinkles. Length 4 inches: 

 heighth 3| inches. 

 Locality. Santa Barbara, Gal. Dr. Newberry. 



PALLIUM, Klein. 



1. P. eslrcllanum. Suborbicular ; lower valve ventricose, slightly undulated ; 

 ribs 17, broad, little prominent, convex, with an intermediate linear rib, from 

 which the larger ribs are separated by an impressed line ; upper valve convex, 

 somewhat undulated, ribs flattened and the intermediate small ribs with a lon- 

 gitudinal impressed line on the lower part of the valve. Height 2 J inches. 



Locality. Estrella valley, Cal. Dr. Newberry. 



2. P. crassicardo. Obtusely ovate or suborbicular, thick ; lower valve 

 ventricose ; ribs 15 16, elevated, back rounded, sides flattened, disks radiato- 

 striate, 9 or 10 on the ribs, intervals of ribs concave, umbo or whole disk at 

 wide intervals having a tendency to be humped and nodose ; upper valve con- 

 vex or slightly ventricose; ears large, equal ; hinge thick, with promineat, 

 acute, oblique teeth ; fosset profound ; muscular impression very large. Height 

 5 inches. 



Locality. Monterey Co., Cal. A. S. Taylor. 



PECTEN, Lin. 



1. Pecten Meehii. Suborbicular, compressed ; ribs 19 not very prominent, 

 convex-depressed on the back, angulated on the sides. Height 6J inches. 



Locality. San Raphael Hills. Mr. Antisell. 



2, P. aUiplectus. Obtusely ovate ; vibs squamose, slender, 9 of them distant 

 profoundly elevated. Height 2} inches. 



Locality. With the preceding. Mr. Antisell. 



PACHYDESMA, Conrad. 



P. Inezana. Triangular, equilateral ; anal side subcuneiform ; teeth robust. 

 Locality. Santa Inez Mountains. Mr. Antisell. 



MULINIA, Gray. 



M. densata. Subovate, ventricose, thick, very inequilateral ; posterior side 

 very short comparatively, contracted ; extremity subtruncated, much above the 

 line of the base; posterior basal margin very oblique and contracted ; anterior 

 end obliquely truncated ; anterior basal margin rounded ; summits prominent, 

 distant ; lateral teeth very robust and prominent ; inner margin entire. Length 

 2^ inches. 



Locality. Santa Barbara, Cal. Dr. Newberry. 



THRACIA, Leach. 



Thracia mactropsis. Subtriangular, subequilateral, ventricose ; anterior side 

 cuneiform or subrostrated, posterior end regularly rounded ; ligament margin 

 very oblique; base regularly and profoundly rounded; umbonal slope abruptly 

 rounded ; summit prominent, posterior to the middle of the valve ; anterior ex- 

 tremity angular. Length 1 inch. 



Locality. Monterey Co., California. Dr. Newberry. 



MYA, Lin. 



Mya Montereyana. Su^oval, slightly ventricose, thin, inequilateral ; summit 

 hardly prominent ; anterior end subtruncated ? posterior end acutely rounded, 



