Io6 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



tubercules, become considerably depressed upon the sides of the shell, 

 curve gently backward, and become more prominent and wider near the 

 outer margin, where the curve is again decidedly forward. The surface of 

 the shell, both on the ribs and in the intervening rounded hollows, shows fine 

 striations which are parallel always to the ribs. The suture line is simple, 

 consisting of a few broadly-rounded saddles and wide lobes having very 

 short branches. The saddles are but little indented, and are bifid with 

 rounded denticles and incisions. Lobes unequally tripartite. 



There appears to be considerable variation in the shells 

 of this species, some of them being much more compressed 

 and nearly without ribs, while others simply lack the ribs 

 and retain their normal thickness. One specimen in 

 which this variation is extreme, in addition to being almost 

 without ribs or tubercules, has its septa so crowded 

 together as to render them nearly indistinguishable, which 

 does not seem to be true of the great majority of speci- 

 mens. Dr. T. W. Stanton, to whom some specimens of 

 this species were submitted, thinks it probably belongs to 

 the genus Sonneratia Bailey; and in recognition of the 

 valuable contributions he has made to the study of West 

 Coast Cretaceous, the above name for this abundant and 

 interesting species is proposed. 



Occurrence. — This shell is common in the vicinity of 

 Horsetown, Shasta County, California, though it has not 

 been reported from corresponding horizons elsewhere. It 

 belongs, therefore, to the upper portion of the Horsetown 

 division of the Cretaceous. 



The type of the species is in the collections of the Uni- 

 versity of California. 



52. Stoliczkia dispar (d'Orb.) Stoliczka. 



cf. Ammonites dispar d'Orb., Pal. Franc. Terr. Cret., I, PI. XLV. 

 Ammonites dispar (d'Orb.) Stol., Pal. Ind., Vol. I, p. 85, PI. XLV. 



The many descriptions of d'Orbigny's species referred 

 to by Stoliczka have not been accessible for comparison, 

 but the identity of the Indian species with one in the col- 

 lections of the University of California from the Shasta 

 beds cannot be doubted. There is so close an agreement 



