REPORT ON THE MONAXONIDA. 151 



larger specimen is 200 mm. in height aud has an average diameter of about 12 mm. 

 Colour in spirit dull, yellowish-brown. Texture tough aud fibrous. Surface extremely- 

 uneven and minutely hispid. Oscula numerous, small and scattered. 



Skeleton. — There is a reticulation of very stout horny fibre, echinated by spined 

 stylote spicules, and having the primary lines cored by smooth styli which may also 

 project freely at the ends of the primary fibre. The secondary fibres appear to be 

 without a spicular core. 



Spicules. — (a) Megasclera ; (l) smooth styli, very variable in size, measuring up 

 to about 0-54 by 0'024 mm., but often much smaller. These spicules occur in the axis 

 and projecting at the ends of the primary fibre ; those at the ends are of large size. (2) 

 Nearly or quite straight, sharply pointed, entirely spined styli (PL XXIX. fig. 13), 

 echiuating the skeleton fibre ; size about 0'072 by O-QOG mm. (6) Mkrosclera ; of one 

 kind only, viz., smooth toxa (PI. XXIX. fig. 13, a) measuring about 0-029 by 0-0016 mm. 



The very characteristic external appearance and the fact that there is only one 

 kind of miscrosclera present, and that a toxite, are, perhaps, the most characteristic 

 features of this species, by which it may readily be recognized. Although it possesses 

 no chetse, yet this species agrees so closely with the genus Clathria in other respects 

 that we have deemed it advisable to include it in that genus ; it is, perhaps, a form 

 that once possessed isochelate microsclera and has now lost them. 



Locality. — Station 163a, April 4, 1874 ; lat. 36° 59' S., long. 150° 20' E.; Bass 

 Strait; depth, 150 fathoms; bottom, green mud. Two specimens. 



Genus RhaphidoiMus, Ehlers (Pis. XXVIII., XXIX., XL VI.). 



1870. Rhaphidophlus, Ehlers, Die Esper'schen Spongien, Erlangen, pp. 19, 31. 

 1875. Eeldiionema, Carter, Ann. and Mag. Nat. Hist, ser. 4, vol. xvi. p. 185. 



This genus difi"ers from Clathria only in the possession of a distinct, dense crust of 

 outwardly projecting, spicules, the difi"erence being one of degree rather than of kind. 



The original diagnosis (loc. cit., p. 31) runs as follows : — " Schwamm aus netzformig 

 vereinigten Balken mit dichter Rindeuschicht aus stumpf-spitzen Nadeln, daruiiter im 

 Gewebe ein Netz von Hornfasern, in welchen und um welche die gleichen Nadeln liegen, 

 ausserdem eingepflanzte gedornte Nadeln, daneben gleichendige Doppelanker und 

 mannigfach gebogene Kieselfaden." 



This diagnosis is based upon a single species, RhaphidopJilus cratitius, Esper, sp., 

 and is perhaps rather too restricted for generic use. The nature of the " Kieselfaden " 

 is elucidated to some extent by the description of the species (loc. cit., p. 19), which 

 speaks of them as " sehr feine haarformige Kieselfaden, welche ungieich lang und 

 mannigfach gekriimmt sind : einfach spangenformig, oder mit wieder aufgebogenen 

 Enden, oder augh S-fdrmig, doch so, dass die Endtheile nicht in eine Ebene liegen." 



