BRYOZOAN FAUNA OF VINCENTOWN LIMESAND 83 



Genotype. — Pdlosecos (Escharinella) muralis Gabb and Horn. 

 1862. 



This new genus is created for the reception of two species appear- 

 ing in the European Danian and in the supposed American equiva- 

 lent: 



Monoporella angustidens Levinsen, 1925 Faxe. 



Escharinella muralis Gabb and Horn, 1862 Vincentown. 



Levinsen, 1925, interpreted the frontal pores as derived from avic- 

 ularia. They can also be interpreted as areolar pores. In the 

 genera Malleatia Jullien, 1903, and Hlppelozoon Canu and Bassler, 

 1923, of the Reteporidae, there are species with cells exhibiting an 

 analogous aspect in having also very small frontal pores and a 

 lyrula. We are therefore classifying this genus in the Reteporidae 

 doubtfully. 



PSILOSECOS MURALIS Gabb and Horn, 1862 

 Plate 15, Figures 2-7 



1SC2. Escharinella muralis Gabb and Horn, Journ. Acad. Nat. Sci. Philadelphia, 



ser. 2, vol. 5, p. 140, pi. 19, fig. 23. 

 1907. Mttcronella muralis Ulrich and Bassler, in Weller, Geol. Surv. New 



Jersey, Paleontology, vol. 4, p. 352, pi. 26, fig. 10 (bibliography). 



Description. — The zoarium is composed of flattened, rather narrow, 

 irregularly dividing branches, with from 4 to 8 rows of zooecia upon 

 each side. The zooecia are distinct, separated by a salient sinuous 

 thread, elongated, oval or fusiform; the frontal is little convex, 

 smooth, perforated sublaterally by 2 to 4 round or rectilinear pores ; 

 it bears proximally an elliptical avicularium with a pivot oriented in 

 the interior of the aperture of the proximal zooecium. The aperture 

 is elliptical, elongated, and bears on its proximal lip a mucron trans- 

 formed rapidly into a small rectangular lyrule. The ovicell is hyper- 

 stomial, closed by the operculum, completely embedded into the 

 thick wall of the distal zooecium, invisible exteriorly. 



Measurements. — 



rj \Lz= 0.6-0.7 mm. . [k=0.12 mm. 



Zooecium \ 7 ._„ Apertura| , „. 



Ife = 0.35 mm. 1/«=0.1 mm. 



Variations. — Gabb and Horn's figure illustrates one of the many 

 variations of this species. These are caused by the vigorous epical- 

 cification of the frontal aided by the presence of separating threads. 

 When the zooecial walls are very thick the threads become thinner 

 and even invisible, whereupon the frontal is very convex. Simul- 

 taneously, the distal avicularium, salient on the young zooecia, be- 

 comes embedded in the aperture and is not visible on the old zooecia 

 of the same zoarium. The primitive frontal pores always persist 

 and are obliterated only by fossilization. 



