K. F. TOMES ON THE GKEAT-OOLITE MAEEEPOEAEIA. 189 



they are either rounded or ovoid, while at the same time they are 

 rather strongly nodulated. 



The calices are very small, and evenly distributed. They are very 

 superficial, excepting on the thinner parts of the branches, where they 

 have greater prominence. They are round and have a small pim- 

 ple-shaped columella. The septa are about twenty-four in number, 

 and have their margins delicately but distinctly papillated. The six 

 principal ones maintain their thickness quite up to the columella ; 

 the next six pass nearly to the columella, and become considerably 

 thinner as they pass inwards ; the remainder are short and small ; 

 but all are of nearly the same thickness at their outer ends. 



The septal costae generally form an angle where they join those 

 from contiguous calices ; but there is very little disposition to the 

 parallel arrangement observable in so many Thamnastrcece, and 

 none of the costae anastomose. 



Diameter of the calices about half a line, distance from the centre 

 of one calice to the centre of the adjoining one three quarters of a 

 line. 



This species may be briefly described as a miniature Tliamnas- 

 trcea Lyelli, so far as the conformation and size of the calices are 

 concerned; but the corallum is probably quite as large as' in that 

 species. In the size of the calices the present species somewhat 

 resembles T. mammosa ; but the septal costae in the latter species 

 anastomose considerably, whereas in T. microjphylla they never do so. 

 Moreover the papillae of the septa in T. micropliylla are very much 

 smaller and more delicate than in T. mammosa. Only one specimen 

 has been observed ; and it was found completely filling a large mass 

 of stone in the quarry near Burford, by Mr. T. J. Slatter, to whom 

 I am indebted for a portion for my use in preparing this paper. 



Thamnaste^a Walto^i, M.-Edw. & Haime, Brit. Eoss. Cor. p. 120, 

 tab. xxv. fig. 4; not Duncan, Suppl. Brit. Eoss. Cor. pt. iii. 

 pi. ii. figs. 6-9. 



The fragment from which MM. Milne-Edwards and Haime drew 

 their description and figure of this species, although possessing dis- 

 tinctive specific characters, was not sufficiently complete to afford a 

 good account of the species. Many well-preserved specimens are in 

 Mr. Slatter's Eairford collection ; and while certain parts of them 

 accord satisfactorily with the above-mentioned description andfigures, 

 other parts are so different that they might easily be mistaken 

 for another species. It may be described as a digitate rather than 

 a dendroid form, some individuals having at first a more or less irre- 

 gular discoid base, from which arises a central dome- shaped promi- 

 nence terminating in two or three finger-like processes. It was 

 probably one of these finger-like processes that furnished material 

 for the original description. The base is sometimes concave and 

 covered with a thick concentrically wrinkled epitheca, completely 

 hiding the basal wall and costae. The newer calices (that is, those 

 on the upper parts of the corallum) resemble those of the specimen 

 which was figured by the original describers ; but the older ones, 



