SPECIES OF CAMERINIDAE BARKER 



327 



Sections show 2l^ to 2% whorls, with 17 to 20 chambers in the 

 final whorl, but as the specimens are badly preserved it is possible 

 that well-preserved adult specimens would show a slightly larger 

 test with more chambers in the final whorl. The septa are seen to 

 be thick, with well-marked canals giving the appearance of double 

 shell walls. The general appearance in both median and transverse 

 sections differs considerably from that of Camerina, there being 

 closer resemblance to PeIlatisj)irelJa as suggested by Hanzawa (1937, 

 p. 115), though the sections fail to reveal the typical apertural char- 

 acters and structure of the shell wall and canal-system of that genus. 

 It is possible that this species, with C. cubensis Palmer and G. ver- 

 munti Thiadens, all occurring in the Upper Cretaceous, should be 

 referred to a new genus, one of the principal features being the 

 presence of a deep peripheral groove not seen in other species of 

 Camerinidae. 



The principal difference between C. dichersoni and C. vermunti 

 (from study of Mexican specimens of the former) seems to be in 

 the form of the septa, which are much thicker and more curved in 

 the former species. Other characters are compared in the following 

 table : 



» CotjT)e. 

 > Average. 



It is seen that the Mexican specimens approximate very closely C. 

 dicJcersoTd^ although the differences between the three species are not 

 great. 



Plesiotypes.—U.S.'^M. nos. 497901 and 497902. 



Other specimens. — U.S.N.M. no. 497900. 



Occurrence. — This species occurs in Mexico in the Upper Cretaceous 

 Cardenas beds exposed in the railroad cuttings near Cardenas, San 

 Luis Potosi, where it is associated with Lepidorhitoides ininima 

 Douville and fMeandropsina rutteni Palmer. This is a similar assem- 

 blage to that reported from Cuba, and to date the species has not been 

 recorded from other localities in the Tampico Embayment. 



