Polyzoa of Mauritius. 77 



gularly heaped ; walls smooth, white, tliick ; orifice orbicular 

 with articular notch ; on one or both sides on a level with 

 the articular notch, a small subcjlindrical avicularian cell 

 with small subtriangular mandible ; scattered over the zoarium 

 large avicularian cells with long pear-shaped mandibles. 

 Ooecia prominent, globose, vitreous, punctate, fertile cells 

 generally with two avicularian cells. 



The form of the orifice in Schizoporella amjjla was made 

 the sole characteristic of a genus ( Oemellipora) by Prof. 

 Smitt (Flor. Bry. pt. ii. p. 37). Mr. Busk retains this 

 genus in his ' Challenger ' Report, but mentions as an addi- 

 tional character the presence of a median avicularium. 

 Schizoporella ampla possesses the orifice characteristic of 

 Gemellipora^ but has, in place of a median avicularium, a 

 similar organ on one or both sides of the mouth. 



Genus Mastigophora. 



Mastigophora Dutertrei, Aud., var. pesanseris. 



Hippothoa pesanseris, Smitt, Flor. Bry. pt. ii. p. 43, pi. vii. figs. 159, 

 160. 



The small avicularia (or vibracula) on each side of the 

 mouth possess the peculiar " web-foot " mandibles. 



In the British form these appendages are slender setae. 

 The difference of form in these appendages is merely varietal. 



Genus GiGANTOPORA. 

 Gigantopora Igncoides^ E-idley. (PI. VII. fig. 5.) 



G. lyncoides was described by Mr. Ridley in his Report on 

 the ' Alert ' Polyzoa (Proc. Zool. Soc, Jan. 1881). 



The type specimen in the British Museum consists of only 

 a few fully developed cells. 



In that specimen there is but little indication of the manner 

 in which the tubular peristome and large pore are developed ; 

 but in the Mauritius specimens the manner of development of 

 these secondary structures is evident. 



The vibraculoid avicularia on each side of the orifice are 

 elevated above the surface of the zooecium, and arch over the 

 oritice, forming a bridge over the latter. By the growth in 

 breadth of the interavicularian portion of the bridge the 

 tubular peristome and " pore " are formed. A calcareous 

 rim grows up round the pore, thus rendering obscure the 

 mode of formation of the latter. 



The primary orifice of the zooecium is subquadrate, the 

 lower border sinuated. 



