814 MR. J. RITCHIE OX iivuROius [May 24, 



its liydrotlit'ca' iind some of the vniieties of tlie latter species 

 (see Broc'li, 190!) h, text-fig, 22). It appi-oaclies most closely 

 C. miU'nnji Haigitt (1909, p. '578), from which it dillers in being 

 smaller in size, in being cylindrical instead of tapering from 

 hydrothecal margin to base, and in lacking distinctly annulated 

 peduncles, with "annulations occasionally extending .some distance 

 (rarely over the entiie body) on the thecal walls," 



1 regard the unnamed specimen, mentioned ;iud figured by 

 Miss Thornely (1908, p. 83, pi. ix. 'tiQ. 5), from Khor Shinab, 10 

 to 12 fiithouLS, in the Soudanese Red )Sea, as l)elonging to this 

 species. 



CuspiuEi.LA cosTATA Hincks, 1868. (Plate LXXVIT. fig. 8.) 



To the short and incomplete description given by Hincks the 

 following observations may be added. The hydrotheca is cylindri- 

 cal for the greater part of its length, but near the base it gradually 

 tapers downwards. Frequently the basal portion of the hydro- 

 theca lies along the object upon which the epizoon is growing, 

 the distal portion bending upwards at an angle, slightly after the 

 manner of Lafoiia scrrata. Within the bent portion the retracted 

 polyp is generally found. Similar bent hydrotheca^ have been 

 described by Dr. Billard from Lt\ Hougne (1904, p. 165). 



The lines of growth held to be characteristic of the .species, 

 and clearly marked in our specimens, are not lines of growth in 

 the ordinary sense, marking the place whei-e new growth has 

 con\menced. They indicate, instead, the margins of earlier hydi-o- 

 thec;e, the opercular fiaps of which occasionally i-emain attached 

 and give an appearance of longitudinal fluting to the succeeding 

 })ortion of the hydrotheca, as is suggested in the terminal seg- 

 ment in Hincks's figures (1868, pi. xl. figs. 5, 5 a). The secondaiy 

 hydrotheca (produced probably on the regenenxtion of an entirely 

 new hydranth) lies within the primary, and for some distance 

 their w\'dls, though in close contact, remain distinct. The tertiary, 

 when such occurs, lies witliin the secondary, and .so on. Thus 

 the terininal segment i.s, as Hincks okserves, " of thinner material 

 than the rest," for its walls are those of a single hydrotheca, 

 while proximal to the uppermost .segment the walls, owing to the 

 telescoi)ing arrangement, aiu considerably .stivngthened. It is 

 noteworthy that the proximal segment is usually of distinctly 

 le.ss calibre than its succes.sors. The opercuhun of the hydrotheca 

 is compo.sed of about 14 or 15 ftiips. 



The hydranth is sti-ongly retractile, retiring on conti-action to 

 the proximal third of the hydi-otheca. It appears to have about 

 six to eight tentacles, which ai-e clotsely set with whorls of large 

 oval nenr.itocysts, the whorls being I'b fje. apart. The average 

 size of the nematcx-ysts in these whorls is 5*2 fi long by 2 /jl 

 })road, but at the tip of the t('i\tacle larger examples occur, 10"5/x 

 long by 5 /x bi'oad. 



No ijono.some was ob.scrved. 



