242 CEYLON PEAEL OYSTER REPOET. 



PLATE III. 



Fig. 1. Ecionema carteri ; R.N. 175. Spicules. 



a., b., pkgiotrirenes, x 52 ; c, plagiotriiene (protrisene T), x 52 ; <?., cladome of c, x 230 ; 

 d., anatriasiie, x 52 ; d'., cladonie of d., x 230 ; e., oxeote, x 52 ; /., microstrongyla, x 230 ; 

 if., chiasters, x 230. 

 2. Ecionema laviniensis ; R.N. 265. Spicules. 



., dichotrine, x 52 ; b., cladome of dichotriaene, seen from above., x 52 ; c., anatriaene, x 52 ; 

 c'., cladome of c, x230; d., oxeote, x 52 ; e., chiasters, x230; /., oxyasters (?), x230; 

 (/., microstrongyla, x 230 ; //., microxeotc (?), x 230. 

 ,, 3. Gcodia penmcmata ; R.N. 223. Arrangement of the skeleton as seen in vertical section, x 52. 



a., a'., dichotrisenes ; b., somal anatriaene; c, reduced cortical anatriaenes ; d., oxea ; c, sterr- 

 asters in cortical layer; e'., young sterrasters in choanosome ; /., large spherasters. 

 3a. Geodia perwicinata ; R.N. 223. Reduced anatriaene, x 230. 

 3l5. Gcodia peruncinata ; R.N. 223. Microscleres. All x 230. 



a., small spheraster (chiaster ?) ; /*., large spheraster ; ''., outline of sterraster, to show relative 

 size. 

 ,, 4. TctiUa pondifcra ; R.N. 230. Spicules. 



".,/'., plagiotria?nes, x52; c, anatriaene, x 52 ; r'., cladome of c, x 230 ; d., protrisene, x52; 

 d'., cladome of d., x 230 ; c, oxeote, x 52 ; /., '/, microxea, x 230 ; h., sigmata, x 230. 

 ,, 5. Tetilla anomala ; R.N. 153. Spicules. 



a., part of protriaene, x 230 ; b., anatriaene, x 52 ; //., cladome of b., x230; c, oxeote, x52; 

 d., sigmata, x 230. 

 6. Tetilla limicola ; R.N. 70. Spicules from body. All x 230. 



a., anatriaene, cladome and part of shaft; b., protriaene, cladome and part of shaft; <., oxeote; 

 d., sigmata. 

 ,, 7. Paratetilla cineriformis ; R.N. 214. Spicules. 



a.-d., modified triaenes, x 230. (The central canal of these spicules is indicated by the dark 

 shading.) '., protriaene, x 52 ; e'., cladome of c, x 230 ;/., anatriaene, x 52 ;/'., cladome 

 of /., x 230 ; '/., oxeote, x 52 ; ;/', i/", ends of ;/., x 230, showing their irregularity in 

 shape and the central canal ; h., sigmata, x 230. 



PLATE IV. 



Fig. 1. Craniella elegans ; R.N. 193. Vertical section, x 28. 



a., cinatriaenes ; b., protri;enes ; CO., cortical oxea; d.m., dermal membrane; emb., embryo; 

 f.c, fibrous layer of cortex; i.c.c., intracortical (sub-dermal) cavities; r.b., radiating 

 spictilebundles of main skeleton. 

 ,, 2. Tapivbane herd/ward ; R.N. 40. Desmas. All x 230. 

 a., b., young monocrepid desmas; c, adult desma. 

 3. Aciculites orientalis ; R.N, 150. Spicules. All x 230. 



(., /., c, young monocrepid desmas; d., adult desma; e., /., strongyla. 

 4. Discodermia emarginata; R.N. 234. Spicules. All x 230. 



a.-d., stages in the development of the tetracrepid desma; c, end of branch of an adult 

 desma; /., very young discotrisene, side view, s, shaft; ;/., adult discotriasne, surface 

 view s, shaft ; //., microrhabds. 

 ., 5. Petromica massalis ; R.N. 257. Spicules. All x 52. 



"., monocrepid desma; b.-d., monaxonid megascleres, showing variation in form. 



