1914] 



Dickerson: New Molluscan Species 



301 



This species resembles Saxidomus nuttalli of the Recent fauna 

 closely. It occurs in an impure limestone in the Martinez Group near 

 a fault contact with the basement complex. It is associated with 

 Cidaris, sp. and Phacoides, cf. muirensis Dickerson. 



Named in honor of Dr. L. F. Noble, who discovered the locality 

 at which this species was obtained. 



Dimensions. — Height, 3-1 mm. ; length, 72 mm. 



Occurrence. — University of California Locality 2249, two and three- 

 fourths miles N80° W of U. S. Geological Survey bench mark (3927 

 ft.) at Shoemaker, Rock Creek Quadrangle, Los Angeles County, Cali- 

 fornia. Martinez Group. 



CERITHIUM BUTTERWORTHI, n. sp. 

 Plate 29, figure 4 



Shell spindle-shaped with about nine nodose, flattened whorls 

 rapidly decreasing in size. The upper five or six whorls are decorated 

 by about nine elongate vertical nodes which gradually become more 

 and more sharply pointed on the later whorls. The apex of the nodes 

 is just below the wavy suture. The lower two-thirds of each spire 

 whorl is covered by slight vertical nodes and rather strong spiral lines 

 which are indistinct on the type specimen. The body-whorl is much 

 larger than the penultimate whorl. Mouth quadrate ; canal defective 

 but it appears to be characteristic of this genus. 



This species is associated with Meretrix(f) , sp. 



Named in honor of Emerson Butterworth, who gave valuable assist- 

 ance in obtaining collections in the Santa Ana Mountains. 



Dimensions. — Length of broken type specimen, 42 mm. ; width of 

 body whorl, 19 mm. 



Occurrence. — University of California Locality 2192, a locality of 

 doubtful Martinez age. This locality is near a Martinez locality which 

 yielded Venericardia planicosia Lamarck. The strata in both locali- 

 ties rest upon Chico conglomerates. They dip slightly to the west 

 and are small outliers of a once extensive formation. 



MOLOPOPHORUS (?) HOWARDI, n. sp. 

 Plate 29, figures 3« and 36 



Shell of five whorls, ficoid, nodose, with well-marked sulcus upon 

 the body-whorl. The spire whorls form only one-seventh of the entire 

 length of shell. They are nearly immersed in the body-whorls and 



