NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
385 
of the ovicell, in its convex anter and in the absence of the large vibraculum which 
according to Waters develops at the side of the aperture in the European species. 
The ovicell of this species is very characteristic, but unfortunately it is very 
rare; in its absence the determination offers some difficulties. It resembles con- 
siderably Ilippomenella rotula y but differs, in the larger aperture (Aa=0.20mm. 
instead of 0.15 mm. exteriorly) and in the small avicularium placed much lower. 
Occurrence. — Vicksburgian (Marianna limestone) : West bank of Conecuh 
River, Escambia County, Alabama (common) ; Salt Mountain, 5 miles south of 
Jackson, Alabama (common) ; Murder Creek, east of Castlebury, Conecuh County, 
Alabama (common) ; near Claiborne, Monroe County, Alabama (common) ; deep 
well. Escambia County, Alabama. 
Cotypes. — Cat. Nos. 6-1267, 64268, U.S.N.M. 
HIPPOMENELLA COSTULATA, new species. 
Plate S6, figs. 14-19. 
Description. — The zoarium is free, more or less cylindrical, most often com- 
posed of six longitudinal rows of zooecia. The zooecia are elongated, distinct, oval, 
separated by a furrow ; the frontal is very convex, finely granulated, surrounded by 
a single line of small triangular areolae, separated by some short, interareolar 
costules. The aperture is little elongated and suborbicular in the interior; on 
the exterior it shows a proximal lip more or less convex and salient ; the peristome 
bears 4 to 6 spines. The ovicell is hyperstomial, much imbedded in the distal 
zooecia, garnished with two perforated areas with a large pore and radial costules. 
The avicularia placed on each side of the aperture are disposed obliquely or trans- 
versally; they are prominent, subtriangular, and are provided with a pivot. 
Measurements. — Aperture [Aa=0.15 mm. . [ Lz=0. 65-0.75 mm. 
(exterior) 1 7u=0.15 mm. . J ° OeCia ife=0.40-0.45 mm. 
Variations. — The two large pores of the ovicell are often divided into two 
parts by a small tongue or by an internal crossbar (fig. 17) ; the costules are some- 
times altered (figs. 18. 19). The proximal lip of the aperture becomes sometimes 
a veritable mucro (fig. 19). The interareolar costules are attenuated (figs. 15, 16) 
or very complete (fig. 18). The avicularia are constant and symmetrical. The 
zoarium may liaise more than six rows of zooecia (fig. 19) and even be incrusting. 
Affinities. — In its ovicell this species approaches Ilippomenella capitimortis ; 
it differs from it in the' presence of the costules on the ovicell, the greater length 
of the avicularia and their lateral place on the side of the aperture, and the pres- 
ence of a single row of areolae (instead of two). 
It differs from Ilippomenella rot.ula in its nonlamelliform zoarium, its some- 
what larger oral dimensions, the finer costules of its ovicell, and the presence of 
spines. 
It differs from Ilippomenella. angustaedes in its transversal or very oblique 
avicularia (and not almost longitudinal), in their symmetry and a single row of 
areolae. 
55S99— 19— Bull. 106- 
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