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 bv 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. 
A *30 
Fig. 173. — Genus Phylactella Hincks, 1880. 
A, B. Phylactella lahrosa Busk, 1852. Two groups of zooe- 
cia, X 30. (After Hincks, 1880.) 
C. Operculum, X 85. 
D. Phylactella punctigera Waters, 1899. Operculum, X 85. 
(C, D after Waters, 1899.) 
at a small distance from the edge. The apertura is surrounded by a peristomie 
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 lahrosa Busk, 1852. 
Range. — Jacksonian — Recent. 
The fossil species of this genus are : 
Phylactella ( Lepralia ) tubiceps Reuss, 1865, Chattian of Germany. 
Phylactella porosa MacGillivray, 1895, Miocene of Australia. 
The recent species are: 
Phylactella ( Lepralia ) lahrosa Busk, 1852. 
1880. Phylactella Hincks, 
British Marine Poly- 
zoa, p. 356. 
The apertura is more or 
less circular; it bears either a 
lyrule or some cardelles. The 
thick band of the operculum is 
