654 MK. A. W. WATERS ON MEMBEANIPORID^. 



Observations on Memhrcmiporidcd. 

 By Arthur Wm. "Waters, F.L.S. 



[Bead 30th June, 1898.] 

 (Plates 47-49.) 



The genus Memiranipora, as now understood, contains more 

 species than any other genus of Bryozoa, as may be seen by a 

 reference to Miss Jelly's Catalogue of Marine Bryozoa, where 

 out of 1696 species 156 belong to Memhranipora. It is, however, 

 not very clear how far either the family or the genus should be 

 limited ; for Hincks, in his ' British Marine Polyzoa,' places 

 Flustra under Flustridae, whereas in the ' Polyzoa of the 

 Adriatic,' 1886, he puts Flustra under Membraniporidse, while 

 Busk puts Flectra iu another family. 



As to the genus Memhranipora, large as it now is, it has been 

 much reduced by various new genera being formed out of it. 

 Among others, the following have been proposed : — Electra, 

 Onychocella, Steganoporella, Micropora, Chaperia, Farcimia, 

 Memhranipoi^ella, Thalamoporella, Amphible strum, Bamplwnotus, 

 Pyripora, JBathypora, Caleschara, Foveolaria, JRhagasostoma, 

 TJiairopora, Graspedozoum, Diploporella, Monoporella, Bijlustra, 

 Tremapora, Feriteichisma, Mollia ; of which a few are generally 

 accepted, while others are not, for the attempts to break up 

 this large family have been numerous and many have been un- 

 successful. 



For a complete study of Memhranipora, comparisons must not 

 be confined to present limitations, and I had hoped to make my 

 work more complete, but now find it better to leave wider 

 generalizations until dealing with related families, and trust the 

 results now laid before the Society may show where further 

 study is required. Each character has been taken separately 

 and tabulated comparisons have been made of the ovicells, the 

 avicularia, the opercula, rosette-plates, and even of the spines. 



MacGillivray places Farcimia, Selenaria, and Lunulites in the 

 family Membraniporidse ; but without expressing any opinion as 

 to where they should be placed, I have thought it better to leave 

 the discussion of these for the present. Groups have been made 

 of species which, based upon similarity of one or more characters, 

 seem to be related, but until a larger number have been 

 anatomically examined and the development studied, we cannot 

 be sure of our grouping. The anatomy of Memhranipora has 



