the Genus Stenopora, Lonsdale. 185 



investment, in spite of its extraordinarily regular development, 

 is of inorganic origin, and is produced by a post-mortem depo- 

 sition of carbonate of lime within the cavities of the tubes. 

 AVe have been led to this conclusion principally by two con- 

 siderations. In the first place we found that in one speci- 

 men of S. cn'nifa, as above described, this secondary lining of 

 the tubes had no existence at all (PI. IV. fig. 4). In the 

 second place we found tliat in another specimen of the same 

 species this singular brown lining was present, but was irre- 

 gular in its development, terminating in a ragged free edge 

 where it surrounded the visceral chamber. We may therefore 

 regard the figures in PI. IV. as belonging to one and the same 

 species — those of the type-specimen (tigs. 1-3) having under- 

 gone this curious process of mineralization, while those of the 

 specimen in the " M^Cormick collection " (figs. 4 and 5) are free 

 from this. Such other differences as may be observed between 

 these two sets of sections (apart from the absence or presence 

 of this investment) are not only slight, but are easily explained 

 by the fact that those of the type specimen are from the axis 

 of the corallum, while those of the second set are from the 

 peripheral region. 



Formation and Locality/. Permo-Carboniferous (?). The 

 type-specimen is from Illawarra, New South Wales. In addi- 

 tion to tlie type-specimen the JBritish Museum contains two 

 specimens, in precisely the same state of preservation as the 

 type, collected by Dr. M'Cormick during the voyage of the 

 ' Erebus ' and ' Terror ' in either Tasmania or New South 

 Wales. These specimens are distinctly sublobate in form, 

 and it is from one of these that the sections represented in 

 figs. 4 and 5, PI. IV., have been taken. Other specimens of 

 this species contained in the collection of the British Museum 

 are as follows : — (1) Two specimens from Wollongong, New 

 South Wales, one of which exhibits the characteristic nodular 

 appearance presented by so many of the fossils of that locality. 

 In all essential respects these specimens resemble the type- 

 specimen, one being massive and the other sublobate. (2) 

 Three silicified specimens, from Eaglehawk Neck, Tasmania. 

 We have examined thin sections of one of these, and have 

 little hesitation in identifying them with S. cnnita ; but their 

 state of preservation is very poor. (3) A small siliciiied 

 specimen, believed to be from Point Puer, Tasmania. 



Stenopora ? gracilis^ Dana, sp. 



Chatetes gracilis, Dana, Wilkes' U. S. Explor. Exped. vol. x. Geology 

 (1849), p. 712, Atlas, t. ii. Hgs. 10, 10 a-e. 



Spec. char. " Ramose, branches slender, 1^ to 3 lines 



