NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



573 



The special ovicell which Waters called recumbent is placed on the distal 

 part of the zooecium itself between the apertura and the distal zooecium. Viewed 

 laterally it appears attached like a sack on the back of a porter. Evidently it is 

 also more or less supported on the distal zooecium, but frequently it is completely 

 separated from it. In its form, position, and large opening it is eminently adapted 

 to the size of the larvae. 



We know but little of the opercular system. The three opercula which we 

 know have been figured by Waters. 



The determination of the species presents some difficulties. The tremopores 

 and the areolae are very small ; they become obliterated quite easily and the true 

 nature of the frontal is diffi- 

 culty discernible. 



For the classification of 

 the genera we apply always 

 the same principal functions, 

 working of the operculum. 

 compensatrix, calcification. 

 This classification may not al- 

 ways be definite, nor complete 

 for we have only fossil forms 

 at our disposition. 



Generally the ancestrula 

 is a very small zooecium pro- 

 vided with a very large ellip- 

 tical aperture. 



Genus PHYLACTELLA Hincks, 1880. 



1880. Phylactella HINCKS, 

 British Marine Poly- 

 zoa, p. 356. 



FIG. 173. Genus Phylactdla Hincks, 1880. 



A, B. Phylactdla labrosa Busk, 1852. Two groups of zooe- 

 cia, X 30. (After Hincks, 1880.) 



C. Operculum, X 85. 



D. Phylactdla punctigera Waters, 1899. Operculum, X 85. 

 (C, D after Waters, 1899.) 



The apertura is more or 

 less circular; it bears either a 

 lyrule or some cardelles. The 

 thick band of the operculum is 

 at a small distance from the edge. The apertura is surrounded by a peristoruie 

 more or less funnel-shaped; the peristome is interrupted distally and replaced by 

 a small tongue. The frontal is a tremocyst with very fine pores. No spines. 



Genotype.- Phylactella labrosa Busk, 1852. 



Range. Jacksonian Recent. 



The fossil species of this genus are : 



Phylactella (Lepralia) ttrfnceps Reuss, 1865, Chattian of Germany. 



Phylactella porosa MacGillivray, 1895, Miocene of Australia. 



The recent species are: 



Phylactella (Lepralia) labrosa Busk, 1852. 



