16 
Dr Harmer on the Structure and Glassification 
and others are to be regarded as branching Lepralioid forms. 
Other Cellularine genera, eg. Calwellia and Ichthyaria , are pro- 
bably more nearly related to Microporella, although it is not 
impossible that the median pore has been evolved more than 
once. I agree with Waters in thinking that Ichthyaria cannot 
retain its position in the family Bicell ariidae. Urceolipora dentata 
should perhaps be removed to Calwellia. “ Euthyris ” episcopalis 
should be placed in a distinct genus, characterised in part by its 
conspicuous ovicells, and the fact that both layers of their wall 
are calcareous. Flustra militaris, Waters, appears to belong to 
the same genus, and is probably a Lepralioid form in which most 
of the calcification of the front wall has been secondarily lost. 
The Lepralioid genera are probably to be arranged in two 
divisions (see iv (a) and (b)), according to the manner in which 
the calcareous front wall is developed. 
(viii) The calcareous matter of Cheilostomata is probably 
always covered by an “ epitheca ” limited by a cuticle of chitinous 
or other organic substance. In certain cases this is so conspicuous 
that the generic or specific name has been taken from it ( e.g ., 
Galymmophora, Lepralia vestita). The formation of layers of 
superposed zooecia in Gellepora, etc. appears to take place as the 
result of the separation of the epitheca from the calcareous 
wall, the subjacent space developing into a new zooecium. The 
secondary thickening which the calcareous front wall commonly 
undergoes, and the occlusion of the orifices of the zooecia in the 
older parts of the colony, in certain cases, are probably due to 
the existence of this living membrane external to the calcareous 
matter. The membrane usually passes into the “ raised lines ” 
which may form the outlines of the zooecia. In Euthyris obtecta 
this connexion seems to have been lost, and there is a large, 
continuous, extra-zooecial space on the front and back walls of 
the frond. On the front surface the space is traversed by the 
necks of the flask-shaped zooecia, the orifices lying in the same 
plane as the epitheca. The arrangement closely resembles that 
described by D’Orbigny in one of the Cretaceous family Stegino- 
poridae 1 , but if Jullien is correct in his statements 2 , these forms 
have developed what may be described as a tertiary front wall 
by the growth of certain branched peristomial spines. It is a 
noteworthy fact that the cavity beneath this tertiary wall has a 
floor which resembles the outer surface of a Cribrilina. 
The continuous epitheca of Euthyris obtecta is held at a 
distance from the zooecia by papillae which are calcareous at 
1 Disteginopora ( Thoracophora ) horrida, “ Pal. Fran^aise,” “ Terrains Cr4tac£s,” 
y. 1850—51, p. 237, PL 687 bis, fig. 4. 
2 “Les Costulid^es, nouvelle Famille de Bryozoaires,” Bull. Soc. Zool. France, 
xi. 1886, p. 609. 
