242 CEYLON PEARL OYSTER REPORT. 



PLATE III. 



Fig. 1. Ecumema cartrri : R.N. 175. Spicules. 



a., b., plagiotrisenes, x 52 ; c., plagiotriaene (protriaene 1), x 52 ; c'., cladome of r., x 230 ; 

 d., anatriaene, x 52 ; d'., cladome of d., x 230 ; e., oxeote, x 52 ; /., microstrongyla, x 230 ; 

 g., chiasters, x 230. 

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



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

 c'., cladome of c., x230; d., oxeote, x52; e., chiasters, x230;/., oxyasters (?), x230; 

 g., microstrongyla, x 230; /*., microxeote (t), x 230. 

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



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



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

 3A. Geodia pc.runcinata ; R.N. 223. Reduced anatriaene, x 230. 

 3B. Geodia peruncinata ; R.N. 223. Microscleres. All x 230. 



a., small spheraster (chiaster ?) ; b., large spheraster ; c., outline of sterraster, to show relative 



size. 

 ,, 4. Tetilla poculifera; R.N. 230. Spicules. 



a., b., plagiotriajnes, x 52 ; c., anatriaene, x 52 ; '., cladome of c., x 230 ; d., protriaene, x 52 ; 



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

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



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



d., sigmata, x 230. 

 6. Tetilla Umicola ; 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. Paratctilla cineriformis ; R.N. 214. Spicules. 



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

 shading.) t., protriaene, x52; e'., cladome of c., x 230 ;/., anatriaene, x 52; /'., cladome 

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

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



PLATE IV. 



Fig. 1. Cmniella elfgana; R.N. 193. Vertical section, x 28. 



a-., anatrisenes; b., protrisenes; c.o., cortical oxea; d.m., dermal membrane; einb., embryo; 

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

 spicule-bundles of main skeleton. 



2. Taprobane herdmani ; R.N. 40. Desmas. All x 230. 

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

 3. Arii ulili'f uritntalis ; R.N, 150. Spicules. All x 230. 



a., b., c., young monocrepid desmas ; </., adult desma ; e., /., strongyla. 

 4. Disfodfrmia cnini-ginufa; R.N. 234. Spicules. All x 230. 



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

 desma; /., very young discotrifcne, side view, *, shaft; g., adult discotriaene, surface 

 view x, shaft; /*., microrhabds. 

 ,, 5. I'fl mnica massalis ; R.N. 257. Spicules. All x52. 



a., monocrepid desma; b.-<l., monaxonid megascleres, showing variation in form. 



