1 8o Appendix to Part I. 



slightly oval, and the dividing, tubercnlated ridges sharp ; but in 

 consequence of the outer surface not being exposed, their perfect 

 characters, and the changes incidental upon growth, could not be 

 ascertained. 



The coral is imbedded in a dark gray limestone. 



1. Fenestella ampla, sp. n. 



Cup-shaped ; celluliferous surface internal ; brandies dichotomous, 

 broad, flat, thin; meshes oval ; rows of cells numerous, rarely 

 . limited to two, alternate ; transverse connecting processes some- 

 times cellular ; inner layer of non-cellular surface very fibrous ; 

 external layer very granular, non-fibrous ; gemmuliferous vesicle f 

 small. 



Some of the casts of this coral have a general resemblance to 

 Fenestella polyporata, as represented in Captain Portlock's ' Report 

 on the Geology of Londonderry,' pi. xxii. A. fig. la, Id; but 

 there is no agreement between the Van Diemen's Land fossil and 

 the structure of that species as given in PL xxii. fig. 3, of the 

 same work, or in Mr. Phillips's original figures, ' Geology of York- 

 shire,' part ii., pi. i. figs. 19, 20. A general resemblance also exists 

 between Fenestella ampla and a coral obtained by Mr. Murchison 

 from the carboniferous limestone of Kossatchi Datchi, on the eastern 

 flank of the Ural Mountains, but there is again a marked difference 

 in structural details. 



Fenestella ampla attained considerable dimensions, fragments 

 apparently of one specimen covering an area of 4j inches by 3 

 inches ; and it displays considerable massiveness of outline, the 

 branches at the points where they dichotomise often exceeding the 

 tenth of an inch in breadth. 



In the general aspect of the coral a considerable uniformity pre- 

 vails, but the branches vary in breadth, swelling out greatly near the 

 bifurcations ; nevertheless, there is no marked difference of character 

 between the base and the upper part of the cup, even in the number 

 of the rows of cells. 



In the best state of the cellular surface, which has been noticed, 

 the mouths of the cells are relatively large, round or oval, and are 

 defined by a slightly raised margin ; and an undulating, thread-like 

 ridge winds between them, dividing the interspaces into lozenge- 

 shaped areas. The rows of cells, immediately preceding the bifurca- 

 tion, sometimes amount to ten, and after the separation generally 

 exceed two. The mouths of the lateral rows project into the 

 meshes ; and the transverse connecting processes are sometimes 

 cellular. The interspaces between the mouths, as "well as the un- 

 dulating ridges, are granular, or very minutely tuberculated. In- 

 ternally, the cells exhibit the usual oblique arrangement, overlaying 

 each other and terminating abruptly against the dorsal part of the 

 branch. The perfect casts of the cellular surface give the reverse 



