NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
117 
Variations. — The distal part of the 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 the 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 costulae which might be classified as M embraniporella. 
Typical M embraniporella, 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 M embraniporella, 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 have found only two specimens thus far. 
Affinities. — The small micrometric dimensions and the absence of interzooecial 
avicularia distinguish this species clearly from Hincksina parvavicularia and 
H. meg avicularia. 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 vari ety or closely related new species). 
Cotypes. — Cat. Nos. 63882, 63883, U.S.N.M. 
KEY TO SPECIES OP HINCKSINA. 
! (Large spines having power to unite 2 
I Spines small or absent .. 4 
I Small interzooecial avicularia (L 0.40 mm.) E. parvavicularia. 
Large interzooecial avicularia (L 0.60 mm.) H. meg avicularia. 
No interzooecial avicularia 3 
2 [All of the spines equal H. costulifera. 
(Two distal spines larger H. elegans. 
(Spines absent: zoarium bilamellar H. jaclcsonica. 
| Spines present ; zoarium incrusting 5 
(Mural rim enlarged at the base, opesium crenulated proximally H. ocalensis. 
[Opesium not crenulated 6 
[Zooecia small ( Lz=OAQ-OA5 mm.) ; large ovicells H. smithi. 
<J ' (Zooecia large (L.s=0.45-0.50 mm.) ; small ovicells H. reptans. 
Genus OGIVALINA Canu and Bassler, 1917. 
1917. Ogivalina Canu and 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 eximipora Canu and Bassler, 1917. Jacksonian. 
The zooecia have the usual aspect of those in the family Onychocellidae, but 
the interzooecial onychocellarium is replaced by an interopesial avicularium. 
