160 Eev. T. Hincks's Critical Notes 



* Challenger ' Report Busk includes four genera in the 

 Membraniporidan family. Of these Amphihhstrum and 

 Bijlustra can hardly be regarded as anything but arbitrary 

 groups ; Foveolaria seems to have a claim to rank as a distinct 

 genus. The section of the genus Memhranipora of which M. 

 pilosa is the type is classed as a family (Electrinidee), con- 

 taining a single genus, Electra^ Lamouroux. This is an 

 important change, and seems to be justified by the very 

 striking peculiarities of the type. It may perhaps be a ques- 

 tion whether the new 'Challenger' species Electra cylindracea 

 is entitled to a place in the genus. The absence of an ooecium 

 seems to be characteristic of the other species referred to it. 



MacGillivray has instituted the genus Thairopora for Mem- 

 braniporidan forms in which the orifice is surrounded by a 

 border and is closed by an operculum which works on a 

 distinct hinge. There can be no doubt that this is rightly 

 accounted an important structural change, and a good founda- 

 tion for a generic group. I am unable, however, to agree 

 with Mr. MacGillivray when he refers Micropora Jervoisii^ 

 Hincks, to his new genus *. It has the front wall com- 

 pletely calcified and shows the other characters which distin- 

 guish the genus Micropora f. 



4. Family Microporidse, Smitt (part.). 



Memhraniporiihe, Busk, B. M. Cat. (part.). 



Microporidce, 'Challenger' Report (part.); Hincks, Brit. Mar. Pol. 

 (part.). 



In this family the calcification of the front wall is complete 

 and the operculum rests upon a stony framework, which forms 

 a border round it. It shares the depressed area and raised 

 margins with Memhranipora. One or two very different 

 types of structure have been included in this group. Smitt 

 referred to it both Micropora and Steganoporella^ and I at one 

 time took the same view. But I am now convinced that the 

 forms which are furnished with what Dr. J. Jullien has termed 

 the " double ectocyst " must be separated from Micropora^ and 

 are entitled to stand as a distinct family group. Dr. Jullien's 

 contention :j: that this peculiarity is of such significance as to 

 warrant the distribution of the Chilostomata into two great 

 tribes — those which possess it and those which do not — I am 

 by no means prepared to admit. But there can be no doubt 

 that it has a high morphological interest as a very distinct 



* *' New or little-known Polyzoa. — Part XI.," Trans. Roy. See. 

 Victoria, 1886. 



t " Contributions " &c., * Annals ' for February 1882. 



X " Note sur une nouvelle division des Bryozoaires Cheilostomiens," 

 BuU. de la Soc. Zool. de France, t. vi. (1881). 



