280 Mr H. J. Carter on 



comparatively smooth surface ; while in the Echinonema, as 

 the name indicates, more or less of the pointed end always 

 extends beyond it, echinatingly or in tufts. The oscules or 

 vents are conspicuous in the Rhaphtdonema, while in the 

 Echinonema they are generally inconspicuous, from the 

 excretory systems in the latter being generally smaller and 

 thus more numerous, in accordance with their greater density 

 of structure. 



Thus I have contrasted the Rhaphidonema with the 

 Echinonema because in many instances their forms otherwise 

 are so much alike ; but the structural characters of the E,HA- 

 PHIDONEMA run throughout the order so uninterruptedly that, 

 different as the forms may be (which have chiefly led to the 

 grouping), they will be found to be so constant that, although 

 the order contains a number of species, they may easily be 

 found out under the arrangement I have made, which, for the 

 same reason, requires very little revisionary remark. 



When I inserted the group " Palmata," which is the second 

 on the list, I had not seen Bowerbank^s specimen of the 

 " Mermaid's Glove," now in the British Museum, nor had I 

 identified it with Johnston's type specimen of Halichondria 

 palmata there, by finding that the latter possessed the same 

 peculiar form of anchorate ; so for the present this group can 

 be considered to be represented by only one species, viz. 

 Chalina palmata. 



There are three other forms, in all of which the skeletal 

 acerate is accompanied by the same kind of equianchorate 

 flesh-spicule ; but this is of the common navicular shape, and 

 all come from the neighbourhood of the Cape of Good Hope, 

 as will be more particularly noticed hereafter. 



Of the groups in the third family, viz. the Acervochalinida, 

 I can state nothing decisive, excepting that there are solid forms 

 of Rhaphidonema, but their massive condition, aided only by 

 the characters afforded by their structure and spiculation, so 

 far have not enabled me to identify one in particular ; while 

 the " footnote " to the group " Dictyalia" in my classification 

 {op. et loc. cit. p. 143), whose purport is as follows, adds still 

 more to the difficulties, viz, : — " In some instances the pre- 

 dominance of the keratine element in the Rhaphidonema is 

 exchanged for the predominance of the spicular one in the 

 order Holorhaphidota, when the same species must be 

 placed in one or the other, as the case may be, while the 

 group ' Isodictyosa ' in the latter chiefly offers the species 

 with which those of the Rhaphidonema are most likely to 

 be confounded." But such difficulties are inseparable from a 

 classification made by man to aid his memory, and which 

 nature ignores ! 



