Batopora and its Allies. 91 
while in the larger older zoccia the aperture has a nearly 
straight proximal border, below which there is sometimes a 
large avicularian chamber. It is, however, as a rule, very 
difficult to see the shape of the oral aperture, so that, 
although outlined by the camera lucida, the restoration of 
some of the apertures has been necessary. 
This is very closely allied to O. petiolus, Lonsdale *, and 
he, Stoliczka +, Reuss {, Vine §, and Gregory ||, all show 
the central zocecia the smaller, and speak of the zocecia 
radiating from the centre of the zoarium ; also the text and 
figures indicate that it is depressed, which is not the case in 
the North SJtalian fossils, nor is it always so in the specimens 
of petiolus which I have examined. Various authors have 
referred to an ovicell in O. petiolus, but it is spoken of as 
Wie. 2. 
Crbitulipora excentrica, Seg. 
a> 12) 6. Longitudinal section. x 12. 
c. Transverse section near base. xX 25. 
proximal to the oral aperture, whereas it is distal and 
directed towards the centre of the disk. In my specimens 
of excentrica no ovicells are distinguished, though some 
zocecia have a large suboral avicularium. 
Horizontal sections of eacentrica are extremely interesting, 
as they show the primary very near to the stalk, referred to 
as the pit in Spherophora, Batupora, and Stichoporina. ‘The 
* Dixon’s ‘Geology of Sussex,’ p. 151, pl. i. fig. 10 (1850). 
+ Olig. Bry. von Latdorf, p. 91, pl. iii. fig. 5 (1861). 
t Bry. d. deutschen Unterolig. p. 217, pl. i. figs. 1, 2 (1867). 
§ Vine, “Notes on Brit. Eoc. Poly.,” Proc. York. Geol. Polytech. 
Soc. vol. xi. p. 164, pl. v. fig. 10 (1889). 
| “On the Brit. Paleog. Bry.,” Trans. Zool. Soc. Lond. vol. xiii. pt. vi. 
p. 253, pl. xxxi, fig. 12 (1893). 
