196 BRITISH STROMATOPOROIDS. 



specimens are in a state of preservation suitable for the exhibition of the 

 characters in question. 



Upon the whole, it would appear that the genus Parallelopora is nearly allied 

 to Stromatopora, but that it may be fairly separated from this by the structure of 

 the skeleton-fibre. Iu Stromatopora, Goldf., the skeleton-fibre is minutely porous, 

 being traversed throughout by innumerable small vacuities, which are closely 

 contiguous. In Parallelopora, Barg., on the other hand, the thick fibre is 

 penetrated by irregular canaliculi, and also contains a moderate number of com- 

 paratively large vacuities or pores, which are scattered through the fibre at 

 intervals. As a result of this, tangential sections show a markedly perforate or 

 cribriform character of the fibre, which can commonly be recognised in polished 

 specimens even with a hand-lens, while vertical sections show a similarly perforate 

 aspect, or may exhibit a lattice-like structure. 



Putting aside the peculiar structure of the skeleton-fibre, thin sections of 

 Parallelopora Goldfussii, Barg., nearly resemble in general type those of various 

 species of Stromatopora. The zooidal tubes are excavated in the reticulated 

 ccenosteal tissue, and appear in cross-sections (PL XXV, fig. 4) as rounded or 

 oval or sinuous perforations, while they are seen in long sections (Plate XXV, 

 fig. 5) to be provided with numerous tabula?. The radial pillars are wavy, but 

 are approximately parallel, and are connected at irregular intervals by thick 

 cross-bars. 



In some instances (Plate XXV, figs. 8 and 9) P. Goldfussii, Barg., occurs in 

 the " Caunopora-state," the " Caunopora-tubes " being furnished with funnel- 

 shaped tabula?. 



From P. eapitata, Goldf. sp., which it nearly resembles in general form, the 

 present species is sufficiently distinguished by the much finer texture of the 

 skeletal tissue and the smaller and more closely set zooidal tubes. From 

 P. dartingtonensis, Cart, sp., on the other hand, the present species is separated 

 by its thicker skeleton-fibre, and particularly by the fact that the radial pillars are 

 comparatively stout and irregular, whereas in the former these structures are 

 narrow, close-set, and straight. Moreover, the ccenosteum in P. Goldfussii is 

 comparatively small and is typically spheroidal in shape, while it is massive or 

 laminar in P. dartingtonensis, and may attain a considerable size. 



Distribution. — Parallelopora Goldfussii, Barg., is not uncommon in the Middle 

 Devonian Limestones of the Paffrath district, occurring at Hebborn, Hand, and 

 Steinbreche (near Refrath), the last locality in particular yielding excellent 

 examples. In the Devonian Rocks of Devonshire the species occurs rarely in the 

 pebbles of the Triassic conglomerates, and I have a single doubtful example from 

 Partington. 



