Polyzoa of Mauritius, 75 



apparently derived from Memhranipora by the growth of the 

 lamina over the whole area (excepting, of course, the oper- 

 culum), and by the suppression of the infra-areal portion of 

 the zorecium ; the circuni-areal ridge of Memhranipora would 

 be represented by the raised line round the cell in Micropora. 



In Amphiblestruvi the operculum is still attached to the 

 chitinous covering of the area to however great an extent the 

 lamina may be developed. 



In the opinion of many, to make a separate genus of those 

 forms with the lamina is to make an artificial group. 



Family Microporidae. 

 Micropora coriacea^ Esper. 



Family Steganoporellidse. 

 Steganoporella Rozieri^ Audouin. 

 The Mauritius specimen belongs to the " normal form," 

 with marginal tubercles, bilobate ooecium, without avicularia. 



Family Cribrilinidse. 

 Genus Cribkilina. 

 Gribrilina radiata. 

 Innominate form without avicularia. 



Cribrilina radiata, nqx. jiahellifera, nov. var. (PI. X. fig. 4.) 



The zooecia in almost every respect resemble those of the 

 " innominata " form of Gribrilina radiata, but a considerable 

 modification has taken place in the avicularium. As in the 

 Madeiran variety described by Mr. Hincks, the avicularium 

 is developed as a distinct cell ; but the mandible has a re- 

 markable shape, being broad at the base, then tapering and 

 branching out into two rib-like processes, and from the con- 

 joined bases of the latter a thin triangular chitinous expansion 

 arises. 



Family Microporellidse. 



Stephanopoea, nov. gen. 



Zooecia with semicular orifice, lower margin straight, not 

 dentate, without sinus ; peristome raised posteriorly j from 

 anterior margins of wail thus formed a process is given off 

 on each side uniting in front to form with posterior wall a 

 tubular peristome incomplete below. From lower margin of 

 peristome a broad branched process is given off uniting with 

 processes from other zooscia to form a secondary cribriform 

 roof. Special pore wanting. 



