164 PALAEONTOLOGY OF CALIFORNIA. 



in the young shell ; base sub-flattened. Aperture narrow, outer 

 lip considerably produced posteriorly, thickened and strongly 

 incurved, slightly carinated near the extreme anterior end, both 

 lips bearing numerous small teeth, placed deep in the mouth, and 

 not continued downwards to the margins. Surface smooth, or 

 marked by indistinct longitudinal lines of growth. The young 

 shell is thin, the lines of growth pretty distinct, the aperture 

 broadly expanded in the middle, and apex is submerged. 



A perfect specimen has been obtained in the Tejon Group at Martinez, and Dr. 

 Horn sent me two immature ones from Tejon. 



Gen. Epona, H. & A. Ad. 



C. (E.) MATHEWSONII, n. s. 



PI. 27, Pig. 44, a, b. 



SHELL small, thick, very convex, inequilateral, most convex in 

 the middle and a little above ; the outer lip straighter than the 

 opposite side; ends but slightly produced, anterior end more 

 than the posterior; base convex. Aperture linear, outer lip pro 

 duced behind more than the inner, thickened by a callus, ex 

 panded laterally, especially towards the ends, where the margin 

 is thinner and subacute; inner lip regularly iucrusted, carinated 

 in advance; both lips bearing a few large teeth, those on the 

 inner lip being continued as raised lines, to a considerable dis 

 tance on the face of the body whorl. Surface smooth, the limits 

 of the thickening of the outer lip being pretty well defined. 



Length, .43 inch ; width, .28 inch ; height, .22 inch. 



This beautiful little shell has no relations in the formation. It approaches most 

 nearly the sub-genus Epona of H. and A. Adams, but differs from the more typical 

 species of that group, in the very small degree to which the ends are produced. I 

 have never seen but a single specimen, which I obtained from Mr. Mathewson, 

 who found it in the Tejon Group at Martinez. 



