266 Dr. H. A. Nicholson and Mr. R. Etlieridge, Jun., on 



in such a manner as to leave vacant spaces between the inter- 

 vening unthickened portions. Visceral chamber in the outer 

 portion of the tubes alternately contracted and dilated in cor- 

 respondence with the periodic thickening of the walls just 

 spoken of, but open and subpolygonal in the axial portion of 

 the corallum. Septa obsolete. Tabula? remote, usually 

 placed at corresponding levels in contiguous tubes. Mural 

 pores of small size, not numerous, and irregularly distributed. 



History. The genus Stenopora was proposed and partially 

 described by the late Mr. Lonsdale in an appendix, entitled 

 n Description of six Species of Corals from the Palaeozoic For- 

 mation of Van Diemen's Land," to Dr. C. Darwin's work 

 'Geological Observations on the Volcanic Islands ' *. Of the 

 few characters assigned to it, the only one which can be at all 

 seized upon as of generic value is the so-called periodical 

 constriction of the tubes. Two species were described in 

 detail, Stenopora tasmaniensis and 8. ovata. From the re- 

 marks made by Mr. Lonsdale on the former we gather that the 

 branches sometimes become hollow, and that the tubes in the 

 body of each branch are angular, but after deflection towards 

 the surface they become oval. No tabulae were observed. Some 

 peculiar changes in the surface of the colony were observed 

 by Mr. Lonsdale : for instance, where the mouths of con- 

 tiguous corallites are not in contact they were seen to be 

 separated by foraminated grooves, the latter becoming, as 

 growth progressed, gradually filled up ; the walls then thick- 

 ened, and a row of tubercles were developed along the crests 

 so formed. The mouth afterwards became closed by a lamina 

 projecting from the inner wall. 



In Count P. de Strzelecki's work ' Physical Description of 

 New South Wales, &c.' t, Mr. Lonsdale further described 

 Stenopora, gave additional notes on the two species already 

 mentioned, and added two others, S. informis and S. crinita, 

 both massive forms, the two previously described species 

 being ramose. In the generic description now given the 

 contraction of the corallites " at irregular distances, but in 

 planes parallel to the surface of the specimen," is mentioned, 

 and also the existence of additional interpolated tubes. We 

 may here remark that in this final definition of Stenopora by 

 Lonsdale there is no character which would now be regarded 

 as of generic importance. 



The structure of Stenopora ovata is described at greater 

 length than in the previous notice of this species. In the 

 centre of the branches the tubes are in contact and polygonal, 



* London, 1844, pp. 101-1G9. t London, 1845, pp. 262-200. 



