NORTH AMEIMCAX EARLY TERTIARY BRYOZOA. 485 



Affinities. One may follow, from the zoarial extremity, the formation of the 

 avieularium. In the peristomial sinus first formed there develops a small avieu- 

 larium which increases and is transformed in small, somewhat salient chambers. 



This species differs from I'm-dln irrtyuhii-iis in the frontal granulations and 

 the regular form of the zooecia. 



i>i;-in-i'Cn<'< 1 . Lower Jacksonian (Moodys marl): Jackson, Mississippi (very 

 rare). 



Holotype.C&t. No. 6414-2. U.S.X.M. 



PORELLA CORONATA, new species. 



-I'l.-itp ilj. ti::s. 1.V17. 



Description. The zoarium incrusts bryozoa. The zooecia are Mimewhat elon- 

 gated, little distinct,, rather irregular: the frontal is convex and formed of a 

 tremocyst with large pores in quincunx. The apertura is little visible at the base 

 of a deep peristomie; the peristome is thin, salient, garnished with 1 to 5 small, 

 round avicularia; the lyrula is very small and supports a median avicularium. 

 The ovicell is large, transverse but little salient; it is formed of a large area finely 

 porous and very fragile, surrounded by a little salient collar. The median avicu- 

 larium is very little salient, opening outward and borne on a small lyrula. Some- 

 times there are some small adventitious lateral avicularia. 



-,, . {kpi'=O.Wmm. . fZ2=0.60mm. 



Measurements. .renstomice <, Zooecia , 



[Zpe=0.14 mm. j.fe=0.30mm. 



Variations. The young zooecia (fig. 15) or marginal zooecia are separated 

 by a prominent thread; their avicularium is buried in the peristomie, and the 

 avicularia of the peristome are very small. On the adult zooecia the avicularia of 

 the peristome form a sort of crou-n around the apertura; but their number is quite 

 variable and the formation of the ovicell causes them to disappear (fig. 16) ; they 

 have a pivot. The frontal of the ovicell is very fragile; its absence complicates 

 still more the very irregular aspect of this species. 



Affinities. This species differs from Porella irrr</iil<ir/x and Porclln gramilosa, 

 which also have incrusting zoaria. in the presence of the avicularia on the peri- 

 stome. 



Occurrence. Lower Jacksonian (Moodys marl): Jackson. Mississippi (rare). 



Middle Jacksonian (Castle Hayne limestone) : Wilmington. Xorth Carolina 

 (very rare). 



Cotypes.Ca.t. Xo. G4144, U.S.X.M. 



PORELLA DENTICULIFERA, new species. 



Plate G3. figs. 1-3. 



1>< xrription. The zoarium is hilamellar: the two lamellae are back to back 

 and separable. The zooecia are indistinct: the frontal is little convex and formed 

 of a tremocyst. with pores enormous and little numerous. The apertura (in the 

 interior) is semicircular and quite oblique with a proximal border somewhat con- 



