132 



C. BUTTLER 



deflected basal diaphragms, and are therefore mesozooecia (sensu 

 stricto), but the term exilazooecia is retained for consistency with 

 the genus description. 



Autozooecial wall thickness averages 0.05 mm in the exozone. 

 Wall microstructure is composed of steeply inclined, V-shaped 

 laminae; the zooecial wall boundaries are dark and granular. Some 

 exilazooecia are infilled with laminar calcite close to the zoarial 

 surface. In longitudinal section this infilling consists of broad U- 

 shaped laminae. 



Remarks. Halloporina crenulata, the type species of the genus, 

 has been described from the Black River and Trenton Formations 

 (middle Ordovician) of the U.S. mid-west but has not been recog- 

 nised elsewhere. Only one other species of Halloporina has hitherto 

 been identified: H. pan'a (Ulrich & Bassler, 1904), also from the 

 Black River and Trenton Formations of the U.S. mid-west H. 

 crenulata is distinguished from H. parva in having a larger zoarium, 

 larger rounded zooecial apertures (H. parva has polygonal zooecial 

 apertures) and more abundant exilazooecia. Nothing is known about 

 the range of variafion within either species oi Halloporina. Ulrich & 

 Bassler (1904: pi. xiv) illustrated the two species. Colony size 

 appears to be the only major difference between them as shown in 

 the illustrations. The drawings indicate little difference in zooecial 

 aperture shape; the tangential section of H. crenulata is, however, 

 deeper than in H. parva. A re-examination of the species and further 

 material, is needed for a greater understanding of these species. 



The specimens from Clog-y-fran are identified only as H. cf. 

 crenulata. The identification is tentative due to the presence of 

 occasional diaphragms within the outer exozone. The rounded 

 zooecia and relatively abundant exilazooecia suggest similarity to 

 H. crenulata rather than H. pan'a. 



Order CRYPTOSTOMATA Vine, 1884 



Suborder PTILODICTICTYINA Astrova & Morozova, 1956 



Family ESHAROPORIDAE Karklins, 1983 



Genus GRAPTODICTYA Ulrich, 1882 



Graptodictya bonnemai Bassler, 1911 



Figs 28-29 



1911 Graptodictya bonnemai Bassler: 122, pi. 8, fig. 3. text-fig. 



48. 

 1921 Graptodictya bonnemai jaervensis Bekker: 58, pi. 8, figs 



1^. 

 1952 Graptodictya bonnemai Bassler; Toots: 126, pi. 7, figs 5, 8, 



pi, 8, fig. 3, pi. 9, figs 1, 2, pi. 10, fig. 1. 

 1965 Graptodictya bonnemai Bassler; Astrova: 2252, pi. Ix, fig. 2, 



pi. Ixi, fig. 1. 

 1 970 Graptodictya bonnemai Bassler; Nekhorosheva: 86, pi. viii, 



fig. 1. 



Material. NHM PD 8389-8391, 8392b, 9393. 



Other occurrences. Kuckers Shale (Kukruse Stage, Llandeilo), 

 Baron Toll's Estate, Estonia; Jarve, Kukersite Quarry, Wesenberg 

 Limestone (Kukruse Stage, Llandeilo), Wesenberg, Estonia;Vaigach 

 Island and Pai-khoi (Yugorskiy Stage, Llandeilo/Caradoc), Urals, 

 Russia. 



Description. Zoaria erect with thin branches, on average 1.85 

 mm wide by 0.69 mm deep. The margins of the branches are striated. 

 Mesothecae are thin and sinuous. In the exozone the autozooecia 

 form 90° angles with the mesothecae. Autozooecial apertures are 

 oval in shallow tangential sections and average 0.48 mm by 0.3 mm 



in the exozone. Short superior hemisepta are commonly present. 

 Autozooecial boundaries are slightly serrated. Zooecial wall micro- 

 structure is composed of broadly U-shaped laminae. Exilazooecia 

 and diaphragms are absent. 



Remarks. Graptodictya bonnemai was first described by Bassler 

 (1911: 122) from Estonia, as being very similar to the type species of 

 Graptodictya (G. perelegans). The two species were distinguished 

 by G. bonnemai branching less frequently and having more elongate 

 autozooecial apertures. 



Order FENESTRATA Elias & Condra, 1957 



Suborder PHYLLOPORININA Lavrentjeva, 1979 



Family ENALLOPOROIDAE Miller, 1889 



Genus PUSHKINELLA Lavrentjeva, 1979 



Pushkinella sp. 



Material. NHM PD 8376-8378, 8380-8383. 



Fig. 30 



Description. Zoaria are reticulate and anastomosing; only frag- 

 mentary specimens have been found at Clog-y-fran. No exterior 

 frontal views of the colonies are available because frontal surfaces 

 are all embedded in sediment. 



Fenestrules are oval-rounded, with diameters averaging 0.58 mm 

 by 0.42 mm. Branches are rounded and average 0.38 mm diameter. 



The exozone is distinguished by a change in the orientation of the 

 autozooecia and considerable thickening of the zooecial walls. 

 Autozooecia are rounded in the endozone, becoming rounded- 

 slightly petaloid in the exozone, where they average 0.16 mm in 

 diameter. Across one branch one to three autozooecia are present. 



Wall microstructure is hard to distinguish. In one specimen (PD 

 8378) longitudinal laminar microstructure can be identified. Short, 

 narrow acanthostyles are abundant throughout the colony; in the 

 exozone they occasionally indent the autozooecial apertures. The 

 acanthostyles are composed of a hyaline core surrounded by conical 

 laminae, and are on average 0. 1 mm in diameter. 



Remarks. The genus Pushkinella was previously known only 

 from the Baltic region of the former Soviet Union. Two Ordovician 

 species have been recognised: P. mirabilis Lavrentjeva 1979, and P. 

 robusta Lavrentjeva 1979, from Estonia, and one Silurian, P. 

 acanthroporoides Pushkin 1976, from Byelorussia. 



The Welsh specimens of Pushkinella are characterised by the 

 anastomosing colony form, the small oval-rounded fenestrules and 

 rounded branches. Autozooecial walls are extensively thickened in 

 the exozone and autozooecial apertures are rounded to slightly 

 petaloid. Short and narrow acanthostyles are abundant. 



The Welsh specimens differ from P. robusta in having more 

 zooecial apertures per branch, and fran P. acanthroporoides in 

 having a greater number of acanthostyles. P. mirabilis has similar- 

 sized apertures and acanthostyles to the Welsh material, but differs 

 in having occasional basal diaphragms, which are absent in the 

 Welsh specimens. 



Family PHYLLOPORINIDAE Ulrich, 1890 

 Genus PHYLLOPORINA Foerste. 1887 



Phylloporina sp. 



Material. NHM PD 8384. 



Fig. 31 



