90 Dr. H. A. Nicholson on the 



sections of the branches (PI. V. fig. 5), the corallites are ver- 

 tical, diverging slightly outwards towards their summits, and 

 then turning abruptly, and nearly at right angles, to reach the 

 surface. In the vertical portion of their course the corallites 

 have thin undulating walls, and are destitute of tabulae. In 

 the outer horizontal portion of their course the corallites have 

 thicker walls, are provided with delicate remote tabulas, and 

 are interspersed with smaller tubes furnished with numerous 

 close-set tabulse. The increase of the tubes is by fission. 

 Though more closely allied in its general features to C. 

 tuinidus, Phill., than to any other species of the genus, 

 G. Jamesi is shown by microscopic sections to be perfectly 

 distinct. The former species is distinguished by the fact 

 that the corallites do not turn at right angles to gain the 

 surface, but curve gradually outwards, by the presence of 

 remote tabulse in the central corallites and the almost total 

 absence of tabulae in the corallites in the external portion of 

 their course, and, lastly, by the fact that the numerous inter- 

 stitial tubuli do not seem to be provided with tabulse. 



Chcetetes gracilis^ James. 

 Cheetetes gracilis, Nich. op. cit. p. 198, pi. 21. figs. 8, 8 b. 



The internal structure of this species is likewise very distinct 

 and characteristic. In long sections (PI. V. fig. 13) the tubes 

 in the central portion of the branches are seen to be nearly 

 vertical, slightly undulating, with thin walls, and crossed here 

 and there by an occasional tabula. As they approach the sur- 

 face the corallites bend gently outwards, becoming much more 

 strongly undulated, with thickened walls, and increasing in 

 number rapidly by fission. In the outer portion of their course 

 the larger corallites are furnished with a few remote tabulae, 

 whilst the smaller corallites have a considerable number of 

 these structures. In tangential sections, taken close to the 

 surface, the corallites are seen to be oval or rounded, with ex- 

 tremely thick walls, and having a number of very minute, 

 circular, interstitial tubuli interspersed amongst them. This 

 form is at once distinguished from Chmtetes {Monticulipora) 

 Fletcheri, E. & H., amongst other characters, by the thick- 

 walled strongly undulated corallites. 



Chcetetes Fletcheri, Edwards & Haime. 

 Chcetetes Fletcheri, Nich. op. cit. p. 197, pi. 21. figs. 7, 7 a. 

 Though very like C. gracilis, James, in external characters 

 and general appearance, G. Fletcheri is distinguished from that 



