400 



Plate XV. 



Fig. 1 a. Urceolipora nana (Mac Gilliv.), with open 

 operculum. The figure only shows the strong- 

 est of the longitudinal ridges, which keep 

 the covering membrane stretched. Three 

 ooecia are seen. X 40. 



— lb. Two zooecia of the same species with ooecia, 



from the frontal surface. X 40. 



— 1 c. A sagittal section through three zooecia of 



the same species with ooecia. The covering 

 membrane, the lowermost part of which 

 represents the ectoooecium, is too thick, as it 

 has been drawn with a double outline to 

 make it distinct, (look PI. XXIV., fig. 11.). 

 X 40. 



— 1 d. A zooecium of the same species with ooecia, 



from the basal surface. The uniporous ro- 

 sette-plates of the basal surface and of the 

 distal wall are seen. X 40. 



— 1 e. A transverse section through a branch. Two 



zooecia and three of the ridges, which keep 

 the covering membrane stretched, are seen. 

 X 40. 



— 1 f. A transverse section through the proximal 



part of an ooecium and through a portion 

 of the adjacent zooecium. The endoooecium 

 is seen innermost and on each side of its 

 aperture one of the trapeziform projections 

 which contribute to keep the covering mem- 

 brane stretched. On each side of the cover- 

 ing membrane internally is seen the collar- 

 shaped ridge which surrounds the proximal 

 part of the ooecium, and lowest down the 

 separating wall towards the adjacent zooe- 

 cium. Outside the endoooecium the distal wall 

 with its rosette-plates is seen. (On account 

 of incorrect shading it seems to be arched). 

 X 55. 



— 2 a. Euthyris obtecta (Hincks). On the marginal 



zooecia the peculiar processes are seen, by 

 which the covering membrane is kept out- 

 stretched. X 40. 



— 2 b. Four zooecia of the same species, from the 



basal surface. Besides the rosette-plates a 

 number of filiform, calcified elongations are 

 seen. X 40. 



— 2 c. A sagittal section through two marginal zooe- 



cia. The internal lateral processes are visible 

 and also the connections between the cryp- 

 tocyst and the covering membrane. X 40. 



— 2d. Sagittal section through ordinary zooecia. 



X 40. 



— 2 e. The processes of the lateral wall, from the 



uter surface. X 40. 



Fig. 2 



— 3 



— 3 



— 3 c. 



— 4 



— 4 



— 4 



5 a, 



5 b 



f. Operculum of the same species. X 100. 



a. Microporclla marginata (Krauss). X 40. 



b. The distal end of a zooecium of the same 

 species. X 100. 



Four zooecia of the same species, from the 

 basal surface. In addition to the marginal 

 pore-chambers each basal, zooecial surface 

 shows a rosette-plate and an opening for 

 communication with zooecia in the opposite 

 layer. X 40. 



d. The operculum of the same species. X 140. 



e. Radical fibres of the same species. X 40. 



f. A vibracular flagellum of the same species. 

 X 75. 



a. Microporella flabellaris (Busk). X 40. 



b. The distal end of a zooecium of the same 

 species. X 40. 



c. The same species from the basal surface. 

 Besides the basal wall of the pore-chambers 

 the small triangular basal surface of the 

 vibracular chamber is seen lowest down to 

 the right on the four zooecia. On some zooe- 

 cia the basal surface shows a rosette-plate, 

 and on others an opening corresponding with 

 a rosette-plate in an opposite zooecium. 

 X 40. 



d. Radical fibres of the same species. X 40. 



e. The operculum of the same species. X 140. 

 f. The avicularian mandible of the same spe- 

 cies. X 55. 



The first three zooecia of a colony of Micro- 

 porella ciliata (Pallas). The original aperture 

 of the primary zooecium, which is surround- 

 ed by spines, is almost closed to a pore. 

 X 55. 



The aperture of Microporella ciliata. A well- 

 developed vestibular arch is seen and the 

 supporting beam is furnished with a pair of 

 lateral teeth. X 200. 



a. Microporella decorata (Reuss). The zooecium 

 is furnished with three distal pore-chambers, 

 and the curved belts on the ooecium, at the 

 base of which are seen the fine pores of the 

 endoooecium, are canal-like cavities between 

 the endoooecium and the distal calcified part 

 of the ectoooecium. Between these canals, 

 which open through a circle of pores, the 

 two layers of the ooecium have united. X 40. 



b. A portion of the ooecium more highly mag- 

 nified. X 75. 



c. An operculum of the same species. X 100. 

 a. The aperture of Microporella Malusii (Aud.). 



X 100. 



