430 G. HERBERT FOWLER. 



endoderm, light grey ; mesoglcea, dark gray ; space formerly occupied by 

 corallum, dotted. On each side of a central entoccelic septum lies a mesen- 

 tery, external to which is an ectocoelic septum. Corresponding to the mesen- 

 teries are the pseudo-costae (a) in direct contact with the body wall (b. w.), 

 with which the ectocoelic costae are also in contact (a 1 ). The rugse of the 

 mouth-disc (m. d.) are seen in transverse section, supported on solid offsets of 

 mesogloea (v. pp. 9 — 12). 



Fig. 11. Sphenotrochus rtjbescens. — Transverse section at a lower plane 

 than is represented in Fig. 10, A. The body is in contact with pseudo-costae 

 (a), and with both ectocoelic and entoccelic costae (a 1 ). The latter, however, 

 at certain points do not reach the body wall (a 2 ), thus allowing of transverse 

 communication between the longitudinal canals. (The theca has been 

 diminished in breadth by one half.) 



Fig. 12. Sphenotrochus kubescens. — Section through a portion of the 

 ovum and surrounding tissues. The vacuolated ovum, bounded by a thin 

 vitelline membrane, has shrunk in the preservative fluid away from the follicu- 

 lar cells. The latter lie closely appressed to the thin mesogloeal capsule, 

 which is covered by endoderm cells externally (v. p. 11). 



Fig. 13. Stephanaria planipora. — Section through a part of the colony 

 at right angles to the polyps, of which three are included (J, B, C). The 

 rest of the section is composed of the mesenteries and septa (septo-costae) 

 which radiate from them (v. p. 12). 



Figs. 14 and 15. — Seriaiopora tenuicornis, sp. n. (v. p. 14). The 

 drawings for these two figures are due to the skill of Miss Stone. 



