Correspondence — Mr. G. H. Kinakan. 425 



part of the Oawaru formation. They consisted of fragments of 

 species of the genus Isis and of Corallium. These were compared 

 with those from the Australian Tertiaries, and the author inferred 

 that both deposits were formed under similar conditions, and that 

 they were at least homotaxial, whatever their precise geological age 

 might be. 



7. " On some Fossil Corals from the Tasmanian Tertiary De- 

 posits." By Prof. P. Martin Duncan, F.E.S., V.P.G.S. 



The author described a new species of DendropTiyllia possessing 

 very unusual characters, the epitheca replacing the true wall, and 

 giving the specimen a marked Palaeozoic appearance. The fossil was 

 obtained from a Tertiary deposit, and was associated with Placo- 

 trochus deltoideus, a well-marked coral, characteristic of a definite 

 geological horizon in Victoria, namely the lower beds of the Cape 

 Otway section, belonging to the Lower Cainozoic period. For this 

 coral he proposed the name of DendropJiyllia epithecata. A much 

 worn reef-coral was found associated with the above. 



C OIRIKJES IPO ZETIDIEIISrCIE . 



ON THE NOMENCLATURE OF ROCKS. 



Sir, — In " A Handy-book of Eock Names " it was suggested that 

 some of the rocks therein included as granitoid varieties of Liparite 

 " ought probably to be classed among the granitic rocks." 2 This 

 opinion seems also to be shared by Mr. J. W. Judd, F.G-.S., as in his 

 lately published description of the Ponza Islands, 2 he particularly 

 mentions the granitoid rocks of that island and certain others in the 

 Euganean Hills, Hungary, etc., which he considers to be of the same 

 class as the North American rocks, for which Eichthofen ' has 

 suggested the name Nevadite, or granitic-rhyolite. If we accept 

 this name, we add to our granites : 



Nevadite (Eichthofen), a granitic rock, having a more or less 

 crystalline felsitic matrix, inclosing crystals of quartz, one or two 

 felspars (orthoclase and albite or oligoclase), mica or amphibole. 



This granitic rock represents the passage rock between trachyte 

 and normal granite ; similarly, as a siliceous elvanite, among the 

 older rocks, is the passage rock between felstone and normal granite. 

 There has, however, still to be discovered and described, the passage 

 rocks between augite and granite ; and such rocks I suspect to exist 

 in the neighbourhood of Carlingford Lough, Ireland (parts of Cos. 

 Armagh, Down, and Louth). In this area my colleague, W. A. Traill, 

 has found either four or five distinct intrusive granites : first, Newry 

 granite of pre-Carboniferous age ; second, Mourne granite of post- 

 Carboniferous age ; third, elvanite, probably of the same age as the 

 Mourne granite ; and fourth and fifth, granitic rocks, possibly of Ter- 

 tiary age. The latter rocks seem principally to occur in the Carling- 

 ford district on the south of the Lough, and are variable in character ; 

 some being similar in aspect to some of the typical elvanites ; while 



1 A Handy-book of Rock Names, p. 71. London, Robert Hardwicke, 1873. 



2 Geol. Mag. July, 1875, p. 298, et seq. 



