780 NEW GENERA OF MONAXONID SPONGES, 



Axociella cylindrica Ridley and Dendy. 

 (PI. xxxvii., figs. 1, 2, 3; Text-fig. 2.) 



1886. Esperiopsis cylindrica, Ridley and Dendy (16), p. 340. 



1887. Esperiopsis cylindrica, Ridley and Dendy (17), xx., p. 

 79, PL xix., figs. 2, 2a, 2b. 



External features.— The single specimen (PL xxxvii., fig. 4) 

 upon which the following description is based closely agrees in 

 outward habit with the original specimen. It is a sparsely and 

 dichotomously ramose sponge, with relatively long and slender, 

 distally tapered, cylindrical branches, measuring up to-4.5/xin 

 stoutness and up to 128mm. in uninterrupted length. In the 

 present specimen the stalk is missing: that of the original ex- 

 ample measured 187mm. in length, and had a flattened, branch- 

 ing base, 19mm. in diameter. The surface of the sponge is 



region of the skeleton; but on nearing the surface their spicules in- 

 crease greatly in number and also rather considerably in average dim- 

 ensions (attaining in some specimens to upwards of 800 x 30/J. in 

 maximum size) and assume a more and more plumose disposition, finally 

 forming at the extremity of the fibre a scopiform tuft, — while at the 

 same time the spongin-substance gradually diminishes in quantity to the 

 verge of disappearance. The connecting fibres are of a single spicule's 

 length, and contain only one or two spicules. The dermal megascleres 

 proper are, apparently, relatively very few, but their true number and 

 manner of arrangement cannot be ascertained, since, unfortunately all 

 the specimens are in a dried and washed-out condition and entirely desti- 

 tute of dermal membrane ; they are straight to flexuous styli or subty- 

 lostyli, usually with a slightly truncated basal extremity capped with a 

 few indistinct spinules, and ranging from 165 to 350/u. in length and up 

 to 5/a in diameter. In the peripheral region of the skeleton, lying be- 

 tween the main fibres, and directed parallelly thereto, there occur, 



sometimes singly, sometimes several together in a parallel bundle 

 (dragma), — long and relatively slender, usually symmetrically or flexu- 

 ously curved, rhaphidiform oxea: these, — which presumably are deriva- 

 tives of toxa, — appear to vary, both in number and in size, very con- 

 siderably in different specimens, and are possibly sometimes very rare ; 

 in one of the specimens examined they ranged only from about 300 to 

 (very rarely) slightly above {700/J. in length and up to 5/a in diameter, 

 whereas in another they were seldom less than 850/a long and attained 

 a maximum size of 1280 x 9/a. Isochelae palmatae, 12 to 16/a long, and 

 tricurvate toxa, ranging from 25 to rarely upwards of 130/u, in length, 

 and up to 4/x in stoutness, are scattered fairly abundantly through all 

 parts of the interior. 



