284 REVISION OF THE MONAXONID SPONGES, i., 



scleres. Considerable diversity, indeed, exists among them in 

 the character of their surface-elevations, these being either few 

 or numerous, and either rounded (varving from wart-shaped to 

 dome-like) or conical (and then sometimes prolonged each into a 

 filament). But the various differences observed are apparently 

 merely the outcome of individual variation. 



The labelled specimens, excepting those purporting to repre- 

 sent T. conulosa and T. tuberculata, are in fair agreement with 

 the description of the species whose name they bear, as regards 

 outward chaiacters, and it is beyond reasonable doubt that they 

 are authentic examples of those species: while among the remain- 

 ing specimens, there are some which exhibit the external features 

 ascribed to T. tuberculata, and others, again, having the surface 

 provided with tapering conical processes, which presumably are 

 to be identified with 7\ conulosa. Accordingly, I look upon 

 Lendenf eld's four species of Tethyorrhaphis as representing but 

 a single species, which we may call Tethyorrhaphis Icevis. 



In every respect, Tethyorrhaphis loevis resembles a species of 

 Donatia except in possessing, in addition to asters, microscleres 

 in the form of small blunt-ended rods (microstrongyles) densely 

 covered with minute spines, and along with these a number of 

 forms variously intermediate between them and chiasters. 

 Asexual propagation, by means of buds, occurs, and in the same 

 way as in Donatia. The superficial appearance of the sponge, 

 owing to the absence of any trace of pore-grooves, approaches at 

 times very closely to that of T. ingalll var. Icevis; and, in some 

 cases, microscopical examination is necessary before one can say 

 with certainty to which of the two species a given specimen 

 belongs. 



The spicules composing the radial fibres within the choano- 

 some are blunt-pointed, fusiform styli, frequently almost or quite 

 symmetrically ended (i.e., strongyla); their maximum size varies 

 in different specimens from 1850 by 30/x to 2300 by 38/x. Near 

 the surface of the sponge, the fibres expand penicillately, and 

 their fusiform spicules are there largely replaced by shorter, 

 abruptly sharp-pointed, and more cylindrical styli of various 

 lengths down to 280 /x or less. Spicules similar to the latter 



