98 
erably larger autozooids, and some colonies apparently develop 
erect growth (Walter, 1970, pl.10, figs 3-8). 
In view of the paucity of potential characters for grouping Jurassic 
bereniciform cyclostome species into genera, consideration must be 
given to the possibility of using the presence of transverse ridges as 
a generic character. All of the transversely ridged species seem to be 
closely-related and are classified within the Family Plagioeciidae. 
However, they are currently distributed between two or three differ- 
ent genera. Practical problems are associated with the recognition of 
transverse ridges because, although the ridges are sharp and clearly- 
defined in some species (e.g. H. enstonensis), in others (e.g. H. 
baltovensis) they are gradational with irregular growth checks of the 
sort which can be found in a wide range of bereniciform cyclostomes. 
A more complete analysis of character distributions is recom- 
mended before any attempt is made to group transversely-ridged 
species into one genus. 
Genus MECYNOECIA Canu, 1918 
TYPE SPECIES. 
Recent. 
Entalophora proboscidea Milne-Edwards, 1838, 
REMARKS. Although Canu (1918) named E. proboscidea Milne- 
Edwards, 1838, as the type species of Mecynoecia, Canu & Bassler 
(1922: 11) attempted to change the type species to Pustulopora 
delicatula Busk, 1875, stating: “The widespread and abundant spe- 
cies Entalophora proboscidea Milne-Edwards, 1838, was cited as 
the type of the genus by Canu in 1918, but we have changed the 
genotype for the reason that several species with different kinds of 
ovicells are undoubtedly included under this name and it is perhaps 
impossible at present to determine which one Milne-Edwards de- 
scribed’. This amendment is inadmissable under the International 
Rules of Zoological Nomenclature and therefore E. proboscidea 
stands as the valid type species of Mecynoecia (see also discussion 
in Buge 1979b; Walter 1987). 
The probable type specimen of E. proboscidea (Museum Nationale 
d’ Histoire Naturelle, Paris, Risso Collection 5110) has been exam- 
ined by PDT. Although its colony-form corresponds with the general 
usage of Mecynoecia (e.g. by Harmelin 1976), the specimen lacks 
gonozooids, thus making precise characterization difficult, a prob- 
lem considered beyond the scope of the current paper which accepts 
the generic concept as customarily applied. 
Mecynoecia suprabajocina sp. nov. Figs 23-26, 28 
HOLotTyPeE. MUZ PIG 1601/II/11 (Figs 23-25). 
PARATYPES. MUZ PIG 1601/II/9 and 10. 
NAME. Indicating its similarity with M. bajocina (d’Orbigny, 
1850) and the higher stratigraphical occurrence. 
DESCRIPTION. Colony erect, branches cylindrical (vinculariiform) 
and narrow (Fig. 23), 1.0—1.2 mm in diameter, ramifying dichoto- 
mously. Growth tips low cones in profile, with a radial, spoke-like 
arrangement of interzooidal walls, visible when viewed from above 
(Fig. 28). Zooidal budding apparently centred on branch axis. 
Pseudopores densely-packed and subcircular, absent from broad 
bands at the zooidal boundaries (Fig. 24). 
Autozooids with elongate frontal walls, about 1.0 mm long by 
0.21—0.30 mm wide, slightly convex distally but sunken beneath the 
level of the zooidal boundary wall proximally. Apertures widely- 
spaced, circular or a little longitudinally elongate, about 0.12— 
0.14 mm in diameter, sometimes closed by a terminal diaphragm 
U. HARA AND P.D. TAYLOR 
Fig. 23 Mecynoecia suprabajocina sp. nov., MUZ PIG 1601/I/11, 
holotype. Oxfordian, Baltow, Poland. Scanning electron micrographs of 
uncoated branch with a broken gonozooid close to the distal end, x 21. 
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located either atop a short peristome or inclined and positioned 
proximally to the peristomial rim. 
Gonozooids (Fig. 26) with globular distal dilated frontal wall, 
subcircular or transversely elliptical in outline and well inflated. 
Ooeciopore (Fig. 26) located terminally, more or less semicircular, 
distal edge markedly convex relative to the almost straight proximal 
edge, wider than long, about 0.10 by 0.17 mm. Preserved 
ooeciostomes short. 
REMARKS. This new species resembles Mecynoecia bajocina from 
the Upper Bajocian White Sponge Oolite of the Port-en-Bessin area 
of Normandy, and the contemporaneous Microzoa Beds (a facies : 
y 
the Burton Limestone) of Shipton Gorge, Dorset. However, it differs 
from M. bajocina in the structure of the ooeciopore which is almost 
semicircular (Fig. 25) compared to the ooeciopore of M. bajocina 
which is very strongly compressed medially (Fig. 27). In addition, 
the zooidal boundary areas devoid of pseudopores are substantially 
wider in M. suprabajocina than in M. bajocina. Genetic studies of 
living ctenostome and cheilostome bryozoans have shown clearly’ 
that subtle morphological differences signify different species (€.g.. | 
i 
EES OS See ee, 
Thorpe & Ryland, 1979; Jackson & Cheetham, 1990). Although 
comparable studies have yet to be made on Recent cyclostomes, it 1s 
considered reasonable to favour the taxonomic splitting of 
cyclostomes on the basis of small but consistent differences in 
skeletal morphology (e.g. McKinney & Jackson, 1989). 
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