﻿SPONGES.-HALLMANN. 



209 



directions — vertically, obliquely and horizontally — through 

 the sponge-body, and it is these, I presume, which Whitelegge 

 refers to as "columns." The principal spicules (tylostyli) which 

 are relatively very few in number stand singly perpendicularly 

 to the base of the sponge with their heads almost in contact 

 with the substratum ; they occur in no other situation. The 

 accessory styli (acanthostyli), which also are by no means 

 abundant, are, with the exception of a few scattered individ- 

 uals, arranged similarly to the principal spicules. The 

 auxiliary megascleres (tylostyli) are relatively very numerous 

 and are divisible into two sizes, viz., those of lesser length 

 forming the dermal tufts, and those of greater length scattered 

 within the tissues and forming the strands already referred 

 to. The species accordingly appears to have a closer re- 

 lationship to Rhaphidophlus than to Clafhria. The principal 

 tylostyli vary in length from 180 to 440^1, but only occasion- 

 ally exceed 360 }i ; the stoutest are 8 to 9 f< in diameter. They 

 are characterised by a basal region of spination which may be 

 limited to the surface of the tylosis merely, or may extend^ — 

 particularly in the case of the shorter spicules — over the 

 greater portion of the length of the spicule. The largest 

 accessory acanthostyles are 120 ;< long and rarely exceed 

 6 /( in diameter The auxiliary tylostyli may attain a size of 

 4S0 X 4.5 j< ; the dermal tylostyli are apparently never much in 

 excess of 200 /« in length. The slender isochel?e palmate vary 

 in length from 16 to 20 ft ; the toxa are not more than 

 1.5 >/ in diameter and range in length from about200 to 380^1. 



Microciona clathrata, Whitelegge,! though peculiar in some 

 respects, is distinctly a ClatJnia. The statement in the original 

 description that "the skeleton consists of stout horny fibres 

 arranged in plumose columns" is a remarkable error which 

 can only be explained by supposing that the description was 

 based upon a section through the terminal portion of a branch 

 in which transverse fibres were not conspicuously developed. 

 The skeleton is an irregular reticulation of stout and densely 

 horny fibres, which, except in newly-formed branches are so 

 stronglv developed that the interstices of the meshwork may 

 become reduced almost to the point of obliteration. The 

 sponge is, consequently, exceptionally hard and tough. In 

 the interior of the sponge the fibres are plentifully echinated 

 with large accessory acanthostyles ; the superficial fibres are 

 denselv echinated both with accessory acanthosyles and prin- 

 cipal styli which together hispidate the surface. .Amongst 



1 Whitelegge— Austr. Mu«. Mem., iv.. 10. 1907. ji. 493. The name Chithria 

 chtthruta is at present also used for the sponere originally described by 

 O. Schmidt as Tevncin rlnthrof'i. but as this may be itlaced in the genus 

 RJidrhidovhlns; I refrain from changing the name of Whitelegge's species. 



