476 



REVISION OF THE AXIKELLID.i:. 1., 



ill all essential respects with the preceding; and, fuithermpre, 

 the differences (iii.)aud (iv.)are, almost undoubtedly, due merely 

 to tlie fact of the specimen's having been allowed to become par- 

 tially dried before being placed in alcohol. 



The pores are notably larger in 

 size than in the two preceding vari- 

 eties, varying in diameter from 40 

 to 120/x, and are more uniformly 

 distributed (PI. xxvii., fig.3). The 

 dermal layer is from 40 to 90 /i in 

 thickness, and, in the case of the 

 two similar specimens, is closely 

 packed throughout with spirula?. 

 But in R.N. 415, only a superficial 

 layer of the dermis — usually less 

 than 25 II in thickness — is packed 

 with spirulye, the remaining portion 

 being occupied by numerous para- 

 sitic algal cells. 



The skeleton presents no appre- 

 ciable point of difference from that 

 of the typical variety excepting that 

 the radial fibres are generally much 

 longer — their length, in the ex- 

 panded portions of the branches, 

 beinii' about twice the diameter of 

 the axial fune (PI. xxv., fig.3). The 

 fibres attain, at most, a stoutness of 

 70 to 80/x, but are usually much 

 slenderer, and are always ])ro\'ided 

 with a distinct, though thin sheath 

 of pale-coloured spongin. The 

 skeleton, seen in its entirety, is pale golden-yellowish. 



The megascleres of the stalk are scarcely difi'erent from those of 



Text-ti <'.(). 



* Trachydadus dhiitatufi var. c/aratn.^. 

 Ik from the branches. 



Megascleres: «, from the stalk; 



