NORTH AMERICAN EABLY TERTIARY BRYOZOA. 397 



HIPPODIPLOSIA BACCATA, new species. 



Plate 87, Bgs. 5, 6. 



Description. The zoarium incrusts shells. The zooecia are short, little distinct ; 

 the frontal is somewhat convex; it is formed of a tremocyst with widened pores 

 surmounting an olocyst with very small pores; between the tremopores there are 

 some very small pearl-like tuberosities. The aperture is somewhat oval, the point 

 below; the peristome is wide, smooth, a little salient, complete. The ovicell is 

 hyperstomial and very fragile. On the same peristome. and placed laterally, there 

 is a small avicularium (?). 



,, (7><7=0.10 mm. . jZs=0.30mm. 



Measurements. Aperture 7 _.,,. Zooecia \ , nr . n 



Ua=0.10mm. 1/3=0.20 mm. 



Occurrence. Vicksburgian (Byram marl) : Byram. Mississippi (common). 

 Vicksburgian (Red Bluff clay) : Red Bluff, Wayne County. Mississippi 

 (rare). 



Cotypcs. Cat. No. 61277, U.S.N.M. 



HIPPODIPLOSIA STRANGULATA. new species. 



Plate 87, figs. 10-13. 



Description. The zoarium is unilamellar; it incrusts algae or shells. The 

 zooecia are elongated, distinct, fusiform; the frontal is convex and formed of a 

 thick tremocyst with large pores. The apertura is elliptical, quite elongated, a 

 little constricted in its lower parts, and formed of a large anter, separated from a 

 smaller poster by two salient cardelles; it is buried by the development of a small 

 peristomie; the peristome is thin, salient, without spines. The ovicell is large, 

 globular, salient, ornamented with pores somewhat smaller than those of the frontal ; 

 it is hyperstomial, imbedded in the distal zooecium; it opens into the peristomie. 

 In the peristomie itself or on the peristome there is a quite small orbicular avicu- 

 larium. 



J 7; a= 0.20-0.22 mm. . f/,3=0.70-0.77mm. 



Measurements. Apertura 7 A1 Zooecium 7 n on - ,., 



Uffi= 0.14-0.15 mm. I As =0.30-0.35 mm. 



Variations. The micrometric dimensions of this species vary much and are 

 of little use ; this is the habitual rule of species growing upon various kinds of sub- 

 strata; there are some wide zooecia (fig. 11), some narrow zooecia (fig. 10) and some 

 bordered zooecia (fig. 12). 



Exteriorly this species has the aspect of Porclla; it has all the essential char- 

 acters; tremocyst, peristomial avicularium and ovicell opening into the peristomie. 

 The two cardelles alone reveal to us a different hydrostatic system. The reader 

 may be convinced of this by consulting our anatomical tables of the Hippoporinae 

 and Smittinidae and in comparing their compensatrices. Moreover, species of this 

 sort have a chitinous operculum very different from the opercula of Smittinidae, 

 as it is easy to observe, notably in Eschara lamellosa. The absence of the chitinous 

 appendages and of the polypide is often very unfortunate for the paleontologist. 



