NORTH AMKRICAN EARLY TERTIARY BRYO/OA. 117 



T (iriathiifs. Tin- distal part of tho mural rim comprised between the two 

 oral spines presents three important variations. Sometimes it is a thin and 

 spineless portion of the rim, again it supports two spines smaller than tho others. 

 and finally very often it contains a small canal of unknown function. 



The coalescence of opposite spines is very frequent and there are small por- 

 tons of the zoarium bearing costulac which might be classified as Membraniporella. 

 Typical Membraniporella, however, never presents when broken the aspect of the 

 normal zooecia of this species. It would be very interesting to compare the 

 microstructure of these spines with those of the costules of Membraniporella* but 

 the very limited number of specimens found has not permitted this. 



The specimens from the Vicksburgian near Monroeville, Alabama, which 

 incrusted algae and in which the zooecia are hexagonal constitute perhaps a different 

 species or at least a variety; but we hnve found only two specimens thus far. 



Affinities. The small micrometric dimensions and the absence of interzooecial 

 avicularia distinguish this species clearly from Hincksma p an* avicularia and 

 H. megavicularia. The ovicell is extremely rare. 



Occurrence. Middle Jacksonian: Wilmington. North Carolina (common); 

 near Lenuds Ferry, South Carolina (rare). 



Vicksburgian ("Chimney rock" of Marianna limestone): One mile north of 

 Monroeville, Alabama (a variety or closely related new species). 



f'otypes.Q&i. Nos. 63882, 63883. U.S.N.M. 



KEY TO SPECIES OF HINCKSIXA. 



, (Large spines having power to unite. _ .. 2 



[Spines small or absent _. 4 



Small interzooecial avicularia (L 0.40 mm. I __ __H. iiarruriciihn in. 



2. Large interzooecial avicularia (L 0.60 mm. >._ _.#. megavicularia. 



Xo interzooecial avicularia__ _ 3 



[All of the spines equal__ __J?. costulifera. 



[Two distal spines larger. _ ^.H. elegans. 



\ Spines absent; zoarium bilamellar --H. jacksonica. 



[Spines present; zoarium incrusting _. 5 



[Mural rirn enlarged at the base, opesiuiu crenulateil proximally_. _ H. ocalciixix. 

 [Opesium not crenulated.. . 6 



[Zooecia small (7J =0.40-0.45 mm.) : large ovicells -,.H. smith!. 



'' jzooecia large (L~=0.45-0.50 mm.) ; small ovicells ._ .H. reptanx. 



Genus OGIVALINA Canu and Bassler, 1917. 



1917. O'liraliiM CANT: anil BASSLER. Synopsis of American Early Tertiary Cheilostome 

 Bryozoa, Bulletin 96, United States National Museum, p. 16. 



Endozooecial ovicell. Granular cryptocyst. No dietellae. No spines. 

 Genotype. Ogivalina ''''/" >/>i'a Canu and Bassler. 1917. Jacksonian. 

 The zooecia have the usual aspect of those in the family Onychocellidae. but 

 the interzooecialonychocellarium is replaced by an interopesial aviciilarium. 



