REPORT ON THE HEXACTINELLIDA. 291 



manner, and so on — or to anastomose with other neighbouring branches. The meshes of 

 the reticulated tissue are subquadrangular." 



" Spicules of three kinds, namely, skeleton, subskeleton and flesh spicules. Skeleton 

 spicules sexradiate arms spined throughout, pointed in the smallest, inflated at the 

 extremities in the largest specimens. Subskeleton spicules of two forms: — (1) acerate, 

 straight, fusi/oi'm, attenuately pointed, spined throughout, spines all inclined one way, 

 and more or less closely applied to the shaft ; (2) scopidine spicule, consisting of a shaft 

 and head ; shaft cylindrical, abruptly pointed at the free end, quadrangularly inflated 

 at the other, micorspined throughout, most evidently towards the free end ; head con- 

 sisting of four arms, respectively supported by the four angular projections at the end of 

 the shaft, at first remaining parallel or slightly curved towards each other and then 

 expanded ; arm much thinner than the shaft, inflated globularly at the extremity, micro- 

 spined throughout, especially towards the inflation, where the spines are long and 

 inclined backwards, leaving the convexity of the inflation smooth or bald. Flesh spicule 

 a Hexactinellid rosette, each arm bearing four capitate rays, expanded enjleur-de-lis, or 

 without extended arms, the latter being reduced to a central point, from which the rays 

 radiate in all directions so as to present a globular form." 



" Vitreous fibre smooth between the knots, which are globular and spino-tuberculated 

 all over, except where interupted by their union with the fibre, or by the projection of 

 one or more arms of the sexradiate spicule in the form of large spines, thickened or 

 elongated, pointed or inflated at the extremity and spinulated throughout." 



According to Carter the following are the peculiarities of Eurete farreopsis : — " The 

 globular tuherculated knots of vitreous fibre, which, with the centrally developed spine, 

 looks like a bossed omphalic shield, and the globular inflations respectively at the ends of 

 the scopuliue arms very much like a ' bald head.'" 



Character of the Genus. — A system of multifarious dichotomously branched and 

 richly anastomosing tubes of approximately equal diameter, fixed to its substratum by 

 means of several solid or hollow supports which are inferiorly expanded in a plate-like 

 manner. The margin of these oscular openings is not attenuated as in Farrea. The 

 dictyonal framework of beams forming the skeleton consists in all parts of the sponge — 

 even in the latest formed margins of the oscular openings — of several layers, and 

 surrounds more or less regularly formed, in many cases almost square, in others irregularly 

 quadrangular or triangular, meshes with simple or knot-like thickened intersections. On 

 the dermal and ventral surfaces of the framework of beams conical pegs of various 

 length arise from the intersections, and are directed at right angles to the bounding 

 surface. 



The dermal and gastral skeletons consist of pentact hypodermalia and hypogastralia 

 respectively, and of numerous scopul^ provided with knobbed or pointed teeth. 



