326 PROCEEDINGS OF THE NATIONAL MUSEUM vol.86 



was seen to differ very considerably from any other Mexican form 

 examined, being similar in some respects to Camerina icadiai (L. M. 

 Davies, 1927, p. 273, pi. 21, figs. 17, 18; pi. 22, figs. 7-9), from the 

 Eocene of India. With the recent appearance of Hanzawa's (1937) 

 paper on PeUatispireUa it was seen to show close affinities with that 

 genus, and for a time was thought to be allied to P. antiUea Han- 

 zawa. Detailed sectioning shows, however, that though measure- 

 ments agree well with that species, the apertural characters are those 

 of OpercuUna and Camerina^ and no evidence was found of the 

 complex double shell wall characteristic of PeUatispireUa. The canal 

 system seems to be much simpler than is usual in Camerina^ showing 

 many similarities to Pellatisplrella., and the species may be ancestral 

 to that genus, thus giving some slight evidence for the inclusion of 

 PeUatispireUa in the Camerinidae. 



A description of the new species is as follows : Test small, globosely 

 lenticular, completely involute. The ornament is not discernible 

 owing to the very poor state of preservation, with secondary crystal- 

 lization on the exterior. Diameter, 1.5 to 2.0 mm; thickness, 1.0 mm. 



Sections show the test to consist of 2 to 2i/^ whorls, with 7 or 8 

 chambers in the first whorl. 15 or 16 in the second whorl, and in the 

 case of larger specimens (21/2 whorls), 16 or 17 chambers in the 

 final whorl. The initial chamber, which is spherical to subspherical 

 in shape, measures 220/i, to 270/i. in diameter. The walls and septa 

 are very thick, the latter being rather irregular and only slightly 

 curved. The canal system consists of a well-developed marginal cord, 

 as in Rotalia, with few branches (in distinction from the many 

 branching marginal system in Camerina) ; strongly developed septal 

 canals; vertical canals, especially in the umbonal region, are seen in 

 transverse sections. 



Cotypes.—V.^.^M. no. 497899. 



Occurrence. — Basal Eocene, in association with Discocyclina cris- 

 tensis (Vaughan) and Actinosiphon semmesi Vaughan (probably 

 €hicontepec, or the Tanlajas of Muir). Cotypes have been selected 

 from samples from El Cristo Well no. 1, 3,785-3,790 feet. 



7CAMERINA DICKERSONI Palmer 



Plate 20, Figure 3 ; Plate 21, Figube 12 



1934. ICamerina dickersoni Palmer, Mom. See. Cubana Hist. Nat., vol. 8, p. 243, 

 figs. 4, 5, pi. 14, figs. 1, 2, 4, 6, 8. 



Test very small, compressed lenticular, completely involute, with 

 a well-developed keel of clear shell material. The septa are radiate, 

 gently curved, terminating at the umbo in a rather large central boss. 

 Diameter (average for 10 specimens), 1.0 mm; thickness, 0.3 to 

 0.45 mm. 



