382 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
In the interior (fig. 10) the olocyst is in juxtaposition with a tremocyst with 
tubular pores ; the areolae are therefore of the same nature as the tremopores. The 
olocyst in the upper part of the frontal is covered with a pleurocyst in which the 
elements are oriented toward the mucro according to rule (fig. 11). 
Figure 4 represents a monstrosity in which an abnormal bud has caused the 
formation of inverted zooecia; these monstrosities may moreover be perfectly 
oriented but superposed upon other zooecia. This kind of gemmation, which is 
here only a monstrosity, is, on the contrary, the rule in the Celleporidae. 
Affinities. — This species differs from Hip pomenella angustaedes in its aper- 
ture, which is not elliptical exteriorly, in its zoarium of large spreading fronds, 
and in the absence of oral spines. 
It differs from HippomeneTla ineondita in the pores of its ovicell, which are 
larger, less numerous, and more regularly disposed. 
It differs from HippomeneTla capitimortis in its ovicell with many pores 
(instead of two diaphragmecl pores). 
It differs from HippomeneTla eostulata in the absence of fine costules on the 
ovicell and in its much smaller avicularia. 
It differs from all the other Hippomenellae save II. transversata in its broad 
bilamellar zoarium. In the latter species the avicularia are oriented transversally. 
Occurrence. — Lower Jacksonian (Mooclys marl) : Jackson, Mississippi (very 
common). 
Cotypes. — Cat. No. 64077, U.S.N.M. 
HIPPOMENELLA TRANSVERSATA, new species. 
Plate 49. figs. 15-17.- 
Description. — The zoarium is bilamellar. The zooecia are elongated, distinct, 
elliptical ; the frontal is little convex and garnished laterally by a double or triple 
row of triangular areolae separated by very short costules. The apertura is some- 
what elongated, elliptical; two very small cardelles separate a large anter from 
a somewhat smaller poster. The avicularia are placed symmetrically on each side 
of the apertura ; they are small, triangular and oriented almost transversally. 
, . [Aa=0.18mm. 
Measurements. — Apertura \ 7 „ 1 r . 
1 l/a=0.16mm. 
Zooecia 
Lz= 0.80-1 mm. 
7s=0.60mm. 
Affinities. — -Unfortunately we have no knowledge of the ovicell of this species, 
but the peculiar disposition of the avicularia is absolutely characteristic and almost 
unique in the genus. 
The species differs from HippomeneTla tramsversora , in which avicularia are 
in the same place, in the triangular form of the avicularia and in the absence of 
the large oral mucro. 
Occurrence. — Middle Jacksonian (Castle Hayne limestone) : Wilmington, North 
Carolina (rare). 
Cotypes. — Cat. No. 64078, U.S.N.M. 
