PLATE 16. 



Geodia media Bowerbank. 

 Figs. 1-21. 



1-14. — Megascleres; magnified 30; phot. Zeiss, planar 20: 



1-5, 7n, o, 8b, 9y, lOx, 13, 14, from the digitate specimen; 

 6, 7m, p, 8z, 9c, w, lOd, 11, 12, from massive specimens; 



1-6, 11, groups of megascleres from spicule-preparations; 



7, mesoclades with reduced clades; 



8, regular stout amphioxes; 



9, angularly bent amphioxes; 

 10, branched amphioxes; 



12, 14, plagiotiiaenes; 



13, regular, angularly bent, and branched styles, 



a, (Figs. 3-5) large, slender, regular amphioxes; b, (Figs. 1-5, 8) large, stout, regular 

 amphioxes; c, (Fig. 9) large, stout amphiox, strongly angularly bent at one 

 point; d, (Figs. 5, 10) large amphioxes with one simple branch near one of the 

 ends, enclosing a small angle with the axis of the spicule; e, (Fig. 5) large am- 

 phiox with a bifid branch near one end; f, (Figs. 11, 13) large, regular, simple 

 styles; g, (Fig. 13) large, angularly bent styles; h, (Figs. 11, 13) large styles with 

 one simple branch; i, (Fig. 13) large style with a bunch of simple branches near 

 the pointed end; j, (Fig. 2) large angularly bent amphiox with one simple 

 branch; k, (Fig. 13) large angularly bent style with one simple branch; I, (Fig. 6) 

 anatriaenc, probably foreign to the sponge; m, (Fig. 7) mesoplagiomonaene with 

 nearly straight rhabdome; n, (Fig. 7) mesopromonaene ; o, (Fig. 7) mesoplagio- 

 orthomonaene; p, (Fig. 7) mesoplagiomonaene with strongly curved rhabdome; 

 q, (Figs. 1, 12, 14) slender regular plagiotriaenes ; r, (Fig. 5) slender plagiotriaene 

 with unequal clades; s, (Figs. 1-6, 11, 12) stout regular plagiotriaenes; t, (Fig. 12) 

 stout plagiotriaene with one bifid clade; u, (Fig. 3) stout plagiodiaene with one 

 bifid clade; v, (Fig. 1) stout mesoplagiotriaene with long epirhabd (pointing 

 downwards in the figure) ; w, (Fig. 9) large, stout amphiox angularly bent in 

 two places ; x, (Fig. 10) large stout amphiox with one simple branch near the 

 blunt end, enclosing a large angle (of nearly 90°) with the axis of the spicule; y, 

 (Figs. 1, 9) large, stout amphioxes slightly angularly bent at one point; z, 

 (Figs. 6, 8, 11) very large, stout, regular amphioxes. 



15. — The umbilical part of the surface of a sterraster of a massive specimen; magnified 1800; u. v. 



phot. Zeiss, q. monochr. 1.7, q. oc. 10. 



16. — The largest of the massive specimens; natural size; phot. Zeiss, anastig. 480 / 412. 



17. — The digitate specimen; natural size; phot. Zeiss, anastig. 480 / 412. 



18. 19. — Groups of sterrasters from spicule-preparations; magnified 200; phot. Zeiss, apochr. 8, com- 



pens. oc. 6: 



18, of a massive specimen; 



19, of the digitate specimen. 



20, 21. — A sterroid of the digitate specimen; magnified 300; phot. Zeiss, apochr. 4, compens. oc. 6: 



20, the upper surface in focus; 21, the equatorial profile in focus. 



