NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
417 
the cavities observed on the exterior do not perforate it; they limit the zooecia 
between which they are hollowed out. The large frontal pores open into the same 
zooecia (fig. 4) ; the tremopores are tubules; finally the avicularium is a very large 
chamber hollowed in the thickness of the frontal wall. 
The tangential section (fig. 5) reveals the remarkable size of the avicularium, 
a size which must correspond to a powerful musculature ; the frontal is a tremocvst 
with large pores in the form of tubules ; the olocyst which surround the large frontal 
pores show small vacuoles. 
Affinities. — This is the American representative of Didymosella bioeulaia Waters 
of the Priabonian. It differs from this European species in its frontal which is a 
tremocyst and not garnished with lateral areolae. 
It differs from Didymosella ( Porina ) larvalis MacGillivray, 1868, in its much 
more numerous tremopores and in its two pores placed lower. 
“ In recent specimens there is usually a thick epitheca (ectocyst) covering the 
front of the zooecia, but not closing the peristomial pores. It may possibly be a 
Hiantopora .” (MacGillivray.) 
Occurrence. — Vicksburgian (Marianna limestone) : West bank of Conecuh 
River, Escambia County, Alabama (common) ; Murder Creek, east of Castlebury, 
Conecuh County, Alabama (common) ; near Claiborne, Monroe County, Alabama 
(rare) ; 1 mile north of Monroeville, Alabama (rare) ; deep well, Escambia County, 
Alabama (very rare). 
Cotypes. — Cat. No. 62592, U.S.N.M. 
TRYPEMATELLA, new genus. 
Trypemos , in allusion to the numerous perforations of the zoarium. 
The ovicell is hyperstomial and closed by the operculum for the passage of 
the eggs. The apertura is semilunar, with proximal border a little concave. The 
frontal bears some lateral areolar pores (pleurocyst on olocyst). Two large lateral 
avicularia are placed below the apertura. 
Genotype. — Trypematella papulifera , new species. Pleistocene of California. 
The type of this genus will be described in a forthcoming publication. 
Group 4, MICROPORELLAE. 
The orifice of the compensatrix (ascopore) is distinct and at some distance 
from the apertura. The ovicell is hyperstomial and closed by the operculum. 
The presence of a frontal micropore was considered by Hincks in 1880 as an 
important family character, but the comparison of the larvae does not bear out 
this conclusion. 
According to Jullien the ascopore is the orifice of a horn-shaped process allow- 
ing the exterior to communicate with the tentacular sheath. ITarmer and Levin sen 
believed that this was an optical illusion, and that the ascopore is really the orifice 
of the compensatrix. 
55899— 19— Bull. 106 27 
