ON THE BRITISH SPECIES OF ORTSIA. 133 



but not as in the last species ; it is usually lost in the zooecia of 

 the lower parts of the colony. Aperture circular, with no pro- 

 jection on its outer side. Ovicell small^ fairly high in the 

 internode, prominent near its upper end, and falling away very 

 suddenly to the aperture, which lies on the surface of the 

 zooeciura next above the ovicell on the same side of the 

 internode ; this zooecium curves round the back of the ovicell, 

 and always acquires a characteristic relation to the aperture of the 

 latter; this aperture is inconspicuous, and is never borne on 

 a distinct tube. Rootlets resembling those of C. ramosa. 

 (See also measurements on p. 177.) 



C. aculeata. — 



(14) Hassall. — " Cat. of Irish Zoophytes," 'Ann. and Aiag. Nat. Hist.,' 



vol. vi, 1841, p. 170, pi. vii, figs. 3, 4. 



(15) Supp. to ' Cat.,' ibid., vol. vii, 1841, p. 366. 

 (4) Johnston.— P. 285. 



(16) Smitt. — " Bidr. till kann. om Hafs-Bryozoernas utveckling," 



' Upsala Univ. Arsskrift,' 1863, p. 3. 

 Smitt agrees with van Beneden (20) in stating that the ovicells are 

 completely closed, 



(17) JoLiET. — " Cout. a I'hist. Bryozoaires, Cotes de France," ' Arch, 



Zool. Exp. et Gen.,' vol. vi, 1877, p. 286. 

 C. eburnea, var. aculeata. — 



(6) Busk.— P. 4. 



(7) HiNCKS.— P. 421, pi. Ivi, figs. 5, 6. 



(18) JuLLiEN. — " Liste des Bry. rec. a !^tretat," 'Bull. Soc. Zool, 



Prance,' t. vi, 1881, p. 14. 



(19) Vine. — "Rep. on Recent Marine Polyzoa," 'Brit. Association Re- 



port,' Aberdeen Meeting, 1885, p. 588. 

 C. eburnea. — 



(3) Milne-Edwakds.— PI. vi, fig. 2. 



? (20) P. J. van Beneden. — " Rech. sur I'Anat Bryozoaires 



.... Ostende," ' Nouv, Mem. de I'Acad. de Bruxelles,' t. xviii, 

 1845, pi. iii, figs. 12—16. 

 Van Beneden states that the ovicells are closed on all sides ; and 

 this statement is more likely to have been made of C. aculeata (in 

 which the aperture of the ovicell is very inconspicuous) than of C. 

 eburnea. The specimens figured are by no means unlike C. aculeata, 

 but they have no spines. 



