MIOCENE PECTENS. 81 



and is HOW in the collection of the department of geology, Stanford Univer.sity. 

 Named in honor of Dr. James Perrin Smith, professor of paleontology at the 

 Leland Stanford Junior Universitv. 



Miocene (middle?). Roblar, 12 miles from Paso Robles. and on ranch of W. F. 

 Gillis, 1(1 miles southwest of Paso Eobles, San Luis Obispo County (J. P. 

 Smith). 



Miocene (lower). Between Morro and Tore creeks, and on the Lenton ranch, 

 between Morro and Old creeks, San Luis Obispo County (Fairbanks, K. 

 Moran); 30 miles north of Santa Monica and 1 mile from the ocean. 

 Ventura(0 County (K. E. Majnard); Pyramid Mountain, Greenhorn Moun- 

 tains, Kern County (No. 12925, C. S. M. H.) (Watts). 



PeCTEN (LyrOPECTEN) VAWrHAXI n. sp. 

 PI. XXIII, fijjs. ,S, 8(1, and 'ib. 



Description. — Shell averaging about 4n millimeters in altitude, slightly longer 

 than high, inequivalve, equilateral, convex, and showing constrictions with 

 consequent undulations on the right valve and nodose ribs on the left; base 

 regularly rounded; sides nearly straight above; margins smooth. Right valve 

 with 12 prominent convex ribs separated by concave-bottomed interspaces some- 

 what narrower than the ribs; surface of ribs and interspaces sculptured by 

 numerous fine, imbricated, thread-like, radial lines, between which are fine 

 imln'icating concentric lira?, the lines multiplying by intercalation toward the 

 periphery of the disk; hinge line about five-eighths length of disk; ears unequal, 

 the anterior much elongated, rather narrow, and ornamented by 1 very 

 prominent, rounded, sharply imbricated radials and numerous fine imbricating 

 incremental lirre; byssal notch deep; posterior ear about one-half length of 

 anterior, somewhat concave behind, and ornamented by about fi radial and 

 numerous fine incremental lira". Left valve similar to right, but with narrower, 

 sharper ribs and correspondingly broader interspaces; the second, fourth, seventh, 

 tenth, and twelfth ribs from the posterior end are more prominent than the 

 others, and are subnodose at the lines of undulation of the disk; anterior ear 

 similar to that of the right valve but with 2 or 3 more radials. which are less 

 prominent; posterior ear like that of right. 



Dimensions. — Alt. 37 mm.; long. 10 mm.: hinge line about 2.5 nun.; diameter 

 15 mm. 



This beautiful little Pecteiu though allied to /'. inagnolia, P. crassicardo, etc.. 

 is distinguishable by its small size, obviously unequal ears, long and strongly 

 radially sculptured right anterior ear, deep byssal notch, undulating disk, and 

 finely striated, concave-bottomed inter.spaces. This form seems to conjbine the 

 number of ribs of P. magnolia {P. magnolia generally has one to three less), 

 with the sculpture of P. crassicardo var. kamiltoni, the undulations of P. craxsi- 

 cardo, and the long, strongly sculptured, right anterior ear of the typical Chlamys. 

 It appears to be a connecting link between the typical Chhimyx and Lyropecten. 

 17260— No. 47—06 6 



