INTRODUCTION. 
xxxvii 
afford, however, adequate grounds for the separation of the 
Trepostomata. 
The reference of the Mesozoic Cerioporidae and their allies to 
the Trepostomata has not been accepted by Ulrich, who in 1900 
included them in the Cyclostomata. But if Ceriopora, Eeoeropora, 
etc., are to be excluded from the Trepostomata, I fail to see any 
1 s 
b 
f I 
^ f t i i 
) / 
i Z'' , 
) 
n / / 
/ 
.X 
F 10 . o . — Ceramopora niogareusis, liassler. Silurian — Rochester Shale : Rochester, 
N.Y. Vertical tangential section ; x 8. (After Bassler.) 
valid characters sufficient for the retention of that Order. Thus, 
Figs. 5-10 of some sections, reproduced from the works of Ulrich 
and Bassler, show how closely some Palaeozoic genera agree in 
structure with Mesozoic Bryozoa. 
Fio. 6. — Eridotrypanodulosa, Bassler. 
Silurian — Rochester Shale : Lock- 
port, N.Y. Vertical tangential 
section ; x 20. (After Bassler.) 
Fig. 7. — Trematopora debilis, Ulrich. 
Ordovician — Trenton Group : 
Alexander Co. , 111. Vertical section 
of half a stem ; X 18. (After 
Ulrich.) 
Fig. 5 shows that the walls of Ceramopora, though moniliform, 
may remain quite thin to the surface of the zoarium. Fig. 6, of 
Eridotrypa, and Fig. 7, of Trematopora, illustrate Palaeozoic genera 
