220 DE. G. J. HiOT)E o:n- SEPTASTE^A, D'oEBIGirr (1849), 



There are no traces of fission, and increase is by gemmation, the 

 same as in S. Forlesi. 



The typical specimen (incomplete) is 140 millim. in height, 150 

 in extreme width, and 44 millim. in thickness. The corallites vary 

 from 3 to 6 millim. in diameter, hut their average width is 4*7 

 millim. 



The above description of this species is taken from the type form, 

 described and figured by Mr. Lonsdale in the Quart. Jonrn. Greol. Soc. 

 vol. i. p. 497. After considerable inquiry in various quarters * I 

 ascertained that this valuable specimen was in the Museum of King's 

 College, London ; but until I called attention to the fact, it had not 

 been recognized as the specimen figured by Mr. Lonsdale, and at 

 the time of my first seeing it, it was labelled GlypJiastrcea Forhesi. 



It is very evident that in form, mode of growth, and in every 

 other feature but one, this species is closely similar to Septastrcpa 

 Forhesi. The one feature in which it differs is the greater deve- 

 lopment of the third cycle of septa within the calices. This 

 feature, curiously enough, is limited to the calices, for in the 

 lower part of the corallites only the 12 septa of the first and second 

 cycles are developed, as in S. Forhesi so that specimens in which 

 the surface features are partially obliterated cannot be distinguished 

 from this latter species. I have serious doubts whether this one 

 feature may not, after all, be due to a more favourable condition of 

 growth or environment to which this particular specimen has been 

 exposed. It is somewhat remarkable that of the 13 specimens of 

 Septastrcea which have come under my notice, this is the only one 

 which exhibits such a development of the third cycle of septa in the 

 calices ; in all the others this cycle is only indicated by marginal 

 ridges. There is a certain amount of variation in this respect in 

 the specimens referred to S. Forhesi., for in some only 6 septa are 

 developed in the calices, in others 12, and yet no specific distinction 

 can be made ; since in certain specimens both conditions are present. 

 It might therefore be urged that, as Lonsdale's specimen is undis- 

 tinguishable in every other respect from >S'. Forhesi, the difference in 

 this variable feature does not possess specific value. Whilst ad- 

 mitting the force of the argument, I think it is preferable provi- 

 sionally to allow the diff'erence to be specific, and if further evidence 

 should show that it must be regarded as merely due to external 

 conditions, and that there is only one species, then this species must 

 bear Lonsdale's name of sexradiata, since this has the priority of 

 Edwards and Haime's name, Forhesi. 



Lonsdale's description of this species is remarkably complete, pre- 

 cise, and accurate, and cannot be improved upon at the present day. 

 He even noticed that the individual septum was formed of two 

 united laminae, and that the extension of these formed the walls ; 

 the thickening of the wall and septa is pointed out, and the solid 

 infiUing of the upper part of the corallites is compared with that in 



* In this connexion I beg to express my thanks to Leonard Lyell, Esq., M.P., 

 P.G.S., for searching for this specimen in the Collection of the late Sir Charles 

 Lyell, now in his possession. 



