C. BUTTLER 
Figs 16-18 Batostoma clogyfranense sp. nov. 16, NHM PD 8362 (holotype), longitudinal section, x22. 17, NHM PD 8374 (paratype), longitudinal section, 
x30. 18, NHM PD 8362 (holotype); 18a, transverse section, x30; 18b, tangential section, showing infilled zooecia, x37; 18c, tangential section, x86. 
Fig. 19 Batostoma cf. polare Astrova 1965, NHM PD 8324; 19a, longitudinal section, x22; 19b, longitudinal section, x70; 19¢, tangential section, x41; 
19d, tangential section, x96. 
exozone, and mesozooecia are less common in the Russian species. 
Two species of Batostoma have been previously described from 
the Lower Palaeozoic of the Welsh Basin. B. murchisoni was de- 
scribed by Spjeldnaes (1957) from “Horderley’ in Shropshire. This 
species has few diaphragms and mesozooecia, and acanthostyles are 
absent, suggesting that the species may not belong to Batostoma. A 
re-examination of the type material is required. Owen (1962) 
described Batostoma sp, from the Aymestry Limestone (Ludlow 
Series, Silurian), Wenlock. This species has a very small exozone 
and mesozooecia are absent. 
Batostoma cf. polare Astrova, 1965 Fig. 19 
MATERIAL. NHM PD 8324. 
DESCRIPTION. Zoarium erect with narrow cylindrical branches, on 
average 4.5 mm in diameter. 
Autozooecia are parallel to the branch axis within the endozone 
and curve abruptly outwards in the exozone to meet the zoarial 
surface at 90°. The autozooecia within the endozone have thin, 
slightly wavy walls. 
The exozone is thick with an average diameter of 1.1 mm. It is 
recognised by an extensive thickening of the zooecial walls and a 
simultaneous change in zooecial orientation. Autozooecia all origi- 
nate in the endozone, where they are polygonal-rounded in transverse 
section. They become circular in the exozone, as seen in tangential 
sections of branches. Autozooecial diameters average 0.16 mm by 
0.2 mm within the exozone. Diaphragms are present throughout the 
autozooecia, spaced on average 0.06 mm apart in the endozone and 
increasing greatly to 0.38 mm apart in the exozone. The majority of 
these are basal diaphragms, which are deflected orally at their 
junctions with the zooecial walls. Successive diaphragms increase in 
thickness distally along the autozooecia. Several subterminal, 
aborally deflected diaphragms have been recognised at the distal end 
of the colony. 
Mesozooecia are present, although not abundant, and originate in 
the inner parts of the exozone. They have a maximum diameter 
averaging 0.1 mm. In shallow tangential sections they are rounded. 
The mesozooecia contain abundant, thick, orally deflected, basal 
diaphragms, which are spaced on average 0.05 mm apart. 
Acanthostyles are small and abundant with an average diameter of 
0.02 mm and density of 30 per mm”. They originate in the exozone 
