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 Hippomenella arigustaedes 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 Hippomenella incondita in the pores of its ovicell, which are 

 larger, less numerous, and more regularly disposed. 



It differs from Hippomenella capitimortis in its ovicell with many pores 

 (instead of two diaphragmed pores). 



It differs from Hippomenella costulata in the absence of fine costules on the 

 ovicell and in its much smaller avicularia. 



It differs from all the other Hippomenellae save //. fransversata in its broad 

 bilamellar zoarium. In the latter species the avicularia are oriented transversally. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (very 

 common). 



C'otypes.Cnt. 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 transversal! i/. 



JA=0.18mm. . fZs=0.80-lmm. 



Measurements. Apertura, A1 ,, Zooecia< 7 



lte=0.16mm. 1/3=0.60 mm. 



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 Hippomenella transversora, 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). 



Cotypcs.Ca,t. No. 64078, U.S.N.M. 



