NORTH AMERICAN' EARLY TERTIARY BKYOZOA. 



381 



This is truly an American genus and it furnishes us with many important 

 >trati graphic data, as noted in the table below: 



distribution, species of Hippomenella. 



Lower 



Jackson- 



ian. 



Middle 



Jackson- 



ian. 



Upper 



Jufksnn- 



Vioks- 

 burgian. 



HippomeneUa rotula, new species 



Hippontcnclla transrcrsatti. new specie . 

 Hippomttitll'i ttngn.ft'itiit.'!, new species.. 



Hippomcinll' inco < Hi > . aew s]u> ics 



HippomfticU'i captiimortis, new species.. 



Hipimnittull'l cnstitlttti, new species 



Hippomt iii ll'i alifcni, ne\v species 



Ilipftoinftnll'i nitUf.'r i. new species 



Hif.>l.iowt in !h transversora, new species . 



Hifi/tonninll'i punijmx. now species 



HippomeneUa iinct<tt'i, new species 



Hipponnndl'i (iffulata, new species 



flippant t:n i. llu tnhtrosn, new species 



Hippomcncll'i ariculat'i, new species. . .. 

 HippomfncUa crassicoHis, new species... 



Thus the lower Jacksonian is characterized by Hippomenella rotula alone ; the 

 middle Jacksonian by Hippomenella tran&versata, H. angustaedes, H. Hgulata, H. 

 axiculata, and H. tubcrosa; the upper Jacksonian by no species. The Vicksburgian 

 is characterized by H. capitimortis, H. costulata, E. transversora and H. 

 H. roiTienl,!. and H. alifcra range through the entire Jacksonian. 



Group 1. ZOARIUM BILAMELLAR. 

 HIPPOMENELLA ROTULA, new species. 



Plate 49. figs. 4-14. 



Description. The zoarium is free, formed by two lamellae, back to back, and 

 inseparable. The fronds are flat or undulating and may measure 2 centimeters in 

 length. The zooecia are distinct, very elongated, fusiform; the frontal, little con- 

 vex and smooth, is garnished laterally with a double row of areolae much crowded. 

 The aperture is elliptical (in the interior) ; it presents exteriorly a mucronoid 

 convexity very salient on its proximal border; there are two very small cardelles. 

 The ovicell is large, globular, salient, much imbedded in the distal zooecia; the 

 two lateral areas bear three of four large cavities separated by radial projections. 

 The avicularia are small, inconstant, placed laterally below the aperture, provided 

 with a pivot, and with a triangular beak directed toward the base. No spines. 



J/- asurements. Aperture f#a=0.l7 mm. 

 (interior) u<z=0.15 mm. 



Vnriiitions, The micrometric variations are extraordinary; they vary from 

 one to two times. There are sometimes narrow zooecia (fig. 5), again there are 

 wide zooecia (fig. C), and often giant zooecia (fig. 7). The avicularia are absent 

 (fig. 5) or present (figs. 7-9),- generally small. The mucronoid convexity is promi- 

 neiit (fig. 5) or absent (fig. 7). The cavities and the pores of the ovicell are 

 variable in size and in position (figs. 7. 8). 



. fZ3=0.60-1.00mm. 

 Zooecia !/,=0.40-0.50mm. 



