122 Mr. H. J. Carter on two Hexactinellid Sponges. 



importance as the only living representative of the Ventricu- 

 lidse in structure deserves ; nevertheless with what remains 

 of this also there is, as will be seen, abundance left for 

 description and illustration. It has already been described 

 and named by Dr. Bowerbank (Proc. Zool. Soc. May 13, 

 1869, p. 335, pi. XXV. fig. 1), who has given a most faithful 

 illustration of its general structure, to whicli I would refer the 

 reader ; but as neither the general form of the specimen itself, 

 including its elementary composition, has been illustrated, nor 

 the resemblance of the latter to that of the Ventriculida3 pointed 

 out, it seems to me that a more detailed record of this precious 

 little sponge is desirable; and this I have endeavoured to 

 supply. 



Eurete farreojpsis^ n. sp. (PI. IX. figs. 1-7.) 



Vitreohexactinellid. Skeleton. General form bush-like, 

 fixed, sessile, composed of many tubo-branches anastomosing 

 clathrously. Colourless, translucent, becoming white from 

 increasing density of structure towards the base. Branches 

 short, thick, cylindrical, hollow, formed of a delicate thin 

 reticulated wall thickening from the growing margin towards 

 the base or oldest part, widely separate, dichotomous, anas- 

 tomosing as before stated. Orifices of branches respectively 

 circular at first (fig. 2, a), then expanded (fig. 2, J), afterwards 

 funnel-shaped (fig. 2, c), becoming elliptical and contracted ir 

 the centre (fig. 2, d)^ where, by the union of the approximate 

 parts of the margin, two circular orifices are formed whi( 

 grow into two short, round, tubular branches in opposi 

 directions (fig. e), to divide again after the same manner, an 

 so on — or to anastomose with other neighbouring branche^^ 

 when each branch still gives off two others, so that at the 

 point of junction there are four branches instead of two. 

 Where union takes place, either by the approximation of the 

 two opposite parts of the margin or by direct anastomosis, a 

 raphe is formed. General structure of the wall reticular, the 

 longitudinal lines of fibre, which are the largest, remaining 

 parallel while the tube is round (fig. 2, a) , but radiating upon 

 the same plane successively where the orifice becomes ex- 

 panded (fig. 2, c, d). External surface rough, from the projec- 

 tion of the arms of sexradiate spicules which have not become 

 enveloped by the vitreous fibre ; internal surface still rougher 

 from the same cause ; mid structure or wall composed of sex- 

 radiate spicules woven into a reticulated tissue by the vitreous 

 fibre, of which the meshes are subquadrangular, and, as before 

 stated, the longitudinal fibres largest ; varying in thickness 

 from an extremely thin layer of minute sexradiate spicules in 



