1-40 University of California Publications in Geology [Vol. 11 



Family Cardiidae 



Genus CAEDIUM Linnaeus 

 CAEDIUM DICKEBSONI, n. sp. 

 Plate 13, figures 11 and 18 

 Type specimen 11207, Coll. Invert. Palae. Univ. Calif., loc. 1131 



Shell small, ventrieose, subeireular, subequilateral ; beaks central, not very 

 conspicuous, slightly prosogyrous. Dorsal slopes straight or nearly so, the anterior 

 slope apparently being somewhat the longer ; posterior end broadly subtruncate ; 

 anterior end broadly and evenly rounded. Surface sculptured by about thirty 

 prominent radial ribs, with interspaces averaging about the width of the ribs ; 

 tops of ribs on nneroded specimens V-shaped. Surface also covered by medium 

 fine incremental lines, which on the less eroded portions of the shell are rather 

 strongly imbricated. 



Dimensions. — Height, about 55 mm.; length, 6 mm.; diameter of both valves, 

 2.5 mm. 



Occurrence. — University of California locality 1131. 



Named in honor of Dr. E. E. Dickerson, assistant curator of Palaeontology of 

 the California Academy of Sciences. 



This species is very similar in outline and sculpturing to Cardium 

 lincolnensis Weaver; 117 it is somewhat smaller and lacks the narrow 

 thread-like rib, described by Weaver as occurring in the interspaces. 

 Otherwise, the two are very similar. 



CAEDIUM KIEKEEENSIS, n. sp. 

 Plate 12, figure 5 

 Type specimen 11165, Coll. Invert. Palae. Univ. Calif., loc. 2033 



Shell small, inequilateral ; beaks fairly prominent and rather strongly proso- 

 gyrous; anterior dorsal slope very slightly concave; posterior dorsal slope straight, 

 about equal in length to the anterior slope ; anterior end broadly and regularly 

 rounded; posterior end broadly subtruncate, the lower angle of the truncation 

 being obscure. Surface sculptured by from seventeen to twenty V-shaped, nodose, 

 radial ribs, with interspaces averaging somewhat wider than the width of the 

 ribs. Growth lines rather fine. 



Dimensions. — Height, 9 mm.; length, 8 mm.; diameter of one valve, about 

 3 mm. 



Occurrence. — In the tuff beds of the Kirker formation, about one-half mile 

 W of Kirker Creek near the W edge of Sec. 30, T. 2 N, E, 1 E, M. D. B. L. 



This species appears to be quite unique, differing from any of 

 the known Recent or fossil cardiums of the West Coast. 



ii" For original description of Cardium lincolnensis, see Univ. "Wash. Publ., 

 Geol., vol. 1, no. 1, p. 40, figs. 36, 37, 1916. 



