144 PALAEONTOLOGY OF CALIFORNIA. 



D. kevis, n. s. 



PI. 25, Fig. 21, a, b. 



Shell moderate in size, limbs long and slender, section of the 

 smaller limb sub-elliptical, slightly flattened on the ventral side; 

 second limb subcircular, very slightly emarginate by the encroach- 

 ment of the preceding branch; last limb suddenly incurved, and 

 extending to (or beyond?) the middle of the shell. Surface plain, 

 polished, and ornamented only by a few extremely faint undula- 

 tions; the outer or final limb, which is in places very much 

 broken, had one or more constrictions or internal ribs, which do 

 not seem to have been visible on the external surface ; one or 

 two such internal ribs seem to have existed, though in a much 

 less degree, on the middle limb. Septum composed of a dorsal, 

 a ventral, superior lateral, and two supplementary lateral lobes; 

 dorsal lobe deeply divided into two curved branches, each 

 branch bearing one very large spur on the outer side; the body 

 of the lobe with one lateral spur above on each side. Dorsal 

 saddle broad, divided into two branches, that on the upper side 

 being again divided. Superior lateral lobe shorter than the 

 dorsal, more robust, and resembling it in pattern. Lateral saddle 

 like the dorsal, but smaller, and both branches simple. First 

 supplementary lobe very oblique, small and trifurcate. Second 

 straight and simple. Ventral lobe longer than the dorsal, slender, 

 trifurcate, the middle branch toothed, the laterals trifid; above 

 these branches, one large spur on each side. 



Length of specimen (less a little of the smaller end), 2.65 inch ; total length, 3. 

 inch?; length of small limb retained in the specimen, 1.4 inch (= 1.75 inch 

 total?); length of larger limb, 1.6 inch \ (aperture partly destroyed) ; approximate 

 diameter of aperture, .45 inch; diameter in middle of middle limb, .35 inch; 

 diameter in middle of small limb, .12 inch. 



From the Shasta Group, Cottonwood Creek, Shasta County. Not rare; dis- 

 covered by Mr. Mathewson. 



The present species seems very closely allied to Ply. Forbesianum, Stol. ; Pal. Ind., 

 Vol. 3, p. 196, pi. 90, fig. 11, but is twice the size of that shell, and differs in tho 



