CRETACEOUS FOSSILS. 117 



the upper surface of the whorls have their tubercles much larger 

 than the others, and so arranged as to present a cancellated 

 appearance ; those on the side are small, and the tubercles are 

 mere elevated points. Under surface convex, and minutely can- 

 cellated. Umbilicus marked internally by numerous, rather 

 large lines. Margin unknown. 



Figure, natural size. 



Locality: Found at Tuscan Springs, Tehama County, by Dr. J. A. Veatch. 

 Rare. (Division A.) 



A. COGNATA, U. S. 

 PL 20, Fig. 72, and 72 a, b, c, d, e. 



Shell, low conical; whorls six to six and a half, flat or slightly 

 convex and sloping above, acutely carinate on the margin. 

 Mouth quadrangular, oblique. Surface marked by oblique lines 

 of growth and faint revolving lines, sometimes obsolete. Near 

 the margin, on the upper surface, is a prominent isolated rib. 

 Under surface convex in the middle, and concave near the outer 

 margin ; in this concavity is another rib, somewhat larger than 

 the one above. The rest of this side of the shell is like the upper 

 surface. Margin of the umbilicus coarsely crenulatcd. 



This species is very closely allied to the Eocene form, described by Mr. Conrad 

 as Solarium alveatum, and by Mr. Lea as S. bilincatum. In that species (Fig. c) 

 there are two impressed lines, near the margin, above, and two parallel linear ribs 

 below; instead of the single large rib of the present species (Fig. d). 



Figures, natural size. I have seen one specimen with a diameter of one and a 

 third inches. 



Localities: Seven miles south of Martifiez; and near Clayton, above the coal (in 

 Division B.). It is most abundant at Bull's Head Point, near Martinez, where 

 Mr. Mathewson has collected numerous fine specimens, and where I found the 

 individual figured. 



A. IIornii, n. s. 

 PL 29, Fig. 224, and 224 a, b. 



Shell flattened; spire very low, slightly convex: whorls six 

 and a half; suture distinct, impressed ; outer margin of the body 



