th,. vvl barius Howe (fig. 138) apart from external habit, 



j s in ,-.. uil, al ndistinguishabl) identical with that of Flabellaria luteo- 



M., . . fig ; ; On the ground of habil however the 



Iwo remain distin. : I being besom-like (fig 137), the other flabelliform (fig 32) 



[ n ( the mi filaments of the frond are variously gathered into groups which 



divide and anastomose irregularlj somewhat recalling the anastomosis of the lol.es of Avrain- 



!. Rawsoni), all being covered with their corresponding pseudo-cortex 

 the to the interlocking of the contiguous cortical coverings of adjacent 



C. luteo-fuscus Börgesen) <»n the other hand the cortex spreads 

 the whole flatlj expanded mass of the medullary filaments producing an undivided 

 1 In the paper above cited, we described a third species, ( '. excentricus, with 

 ndibuliform hond (fig. 139), collected by Mr. Gardiner in deep water (30 — 47 fathoms) 

 . . Cargados Carajos in the western Indian Ocean. 

 /•". lui . was referred to Udotea by Murray (in Journal of Botany XXVII. 1 - 



and more recently by Howi (in Buil. Torrey Bot. Club XXXIV. 11107, p. 513). h is 

 ver as abundantlj distinct from Udotea as it is from Flabellaria. lts true position is 

 unquestionably in Cladocephalus. 



Cladocephalus therefore contains three species — C. scoparius, C. luteo-fuscus and 

 C. excentricus — unless indeed the first two of these are conspecific 



Cladocephalus differs from Udotea (which in the present monograph we limit to calci- 



fied flabelliform species only) by its uncalcified spongy habit and its densely felted filamentons 



pseudo-cortex arising from branchlets of pseudodateral origin. From Flabellaria it is also quite 



distinct in its peculiar cortex, though, as suggested below, it manifests a certain affinily with 



that genus. From Avrainvillea it differs much in structure, not being composed of a uniform 



felt-work of dichotomous filaments of approximately uniform size and character (as is Avrain- 



villea), but being strongly differentiated into a stratum of large medullary filaments enclosed 



by an external cortical covering of much branched, tapering, and much interwoven filaments. 



We find that Cladocephalus lias a good deal in common with Rhipilia. Both genera 



incalcified, and contain flabelliform and excentrically infundibuliform and zonate species; 



both are characterised by the absence or infrequency of constrictions immediately above the 



dichotomies <<i' their filaments; and both produce pseudo-lateral branchlets. It is interesting 



to notice that the distribution "f each genus is the western Atlantic and the Indian 



in, and that in each genus the Atlantic species have the thicker and the Indian < I 



the smaller filaments. < >n the other hand the differei tween the two genera are 



Rhipilia has no cortical covering; its pseudo-lateral branchlets do not undergo 



ramification, but remain simple and are terminated by a 2— 6-dentate tenaculum or crown. 



Now, these tenaculiferous branchlets of Rhipilia much recall the lateral branchlets which in 



>pecimens of Flabellaria minima serve to bind together the mam filaments 



r ; fig. 125,1. And wc are strongly inclined to regard Flabellaria 



an indication <>f the common ancestr) of /•'. petiolata, Rhipilia and Cladocephalus, 



ir table of affinities (p. 6). 



