40 Mr. H. J. Carter on Specimens 



" recumbent " or horizontal position of the linear spicules, 

 seems to me to be by no means constant and often dependent 

 on circumstances. Even in his description of Hymedesrnia 

 stellata (B. S. vol. ii. p. 150) he uses the term " hispid ;" and 

 in the species Hymedesrnia spinatostellifera, to be hereafter 

 described, I was obliged to seek for an illustration of the entire 

 skeleton-spicule among erect or projecting ones in the more 

 protected parts. 



Dr. Bowerbank admits that all these three genera, which are 

 given one after another in his l British Spongiadse,' are very 

 nearly allied ; and I now feel much inclined to place them all 

 in my group Microcionina, although the Hymedesmina in my 

 classification stand as the ninth group of my Holorhaphidota ; 

 but then the species which illustrate it (p. 197), viz. Hyme- 

 desrnia Johnsonij Bk., and Desmacidon titubans, have not the 

 long, setaceous, acuate, or spinulate spicule which character- 

 izes Dr. Bowerbank's original species (viz. H. radiata and 

 H. stellata, described in 1866, B. S. vol. ii. pp. 149 and 150, 

 and illustrated in 1870, vol. iii. pi. xxviii.), and which, toge- 

 ther with its accompaniments, is characteristic of the kind of 

 Hymedesrnia that 1 should place in my group Microcionina. 

 Hymedesrnia Johnsoni and Desmacidon titubans would be 

 much better placed alongside with Esperina, where they now 

 are in my classification. 



There are, however, species which have not this kind of 

 spiculation, viz. the setaceous acuate, &c, ex.gr. Rhaphidhistia 

 spectabilis ( l Annals,' 1879, vol. iii. p. 300, pi. xxvi. figs. 13, 

 14 a) ; and there are specimens which may be so circum- 

 stanced as never to get beyond a thin lamina, although 

 under other conditions they might grow up into erect forms : 

 such is perhaps Hymedesrnia zetlandica, Bk., judging from its 

 spiculation in the type specimen now in the British Museum, 

 which I should be inclined to regard as allied to Halichondria 

 plumosa, in which case it would come under my Plumohali- 

 chondrina. 



Having premised these remarks it will be understood that 

 although hereafter I shall describe the species of Hymedesrnia 

 found on the Melobesian nodules among the Holorhaphidota, 

 yet I am of opinion that they ought to be under the Echino- 

 nemata,in the group Microcionina, together with the following- 

 ones of Microciona and Hymerhaphia. 



Microciona atrosanguinea, Bk., and M. armata 7 Bk. 



Both these species occur on the Melobesian nodules, now of 

 a red-cinnamon colour, but were probably " blood-red," like 

 the British specimens of the same sponges when alive. Both 



