Rev. T. Hincks on British Puhjzoa. 525 



I am quite prepared for the criticism that some of the 

 divisions which 1 shall projjose are really artificial rather 

 than natural. Must tliere not always be a large element of 

 artificiality in any scheme for distributing into definite groups 

 tlie series of natural forms, so variously interconnected and 

 melting as they do at all points one into the other ? 



Family Membraniporidse, Busk and others. 



The large and heterogeneous group of Cheilostomatous 

 Polyzoa composing this family was ranged by Johnston under 

 the two genera Memhranipora and Lepralia. The latter, 

 comprehending an immense number of species, has been 

 maintained by Busk in its integrity; and he has been followed 

 by many other writers on the Polyzoa. D'Orbigny, in his 

 great work the ' Paleontologie Fran^aise,' has broken it up 

 in part, and distributed its contents through several genera. 

 Gray, in his ' Catalogue of the British-Museum Radiata,' 

 has introduced a number of new groups to include certain 

 sections of the genus Lepralia^ a few of which have every 

 claim to stand, while a large proportion are founded upon 

 trivial characters and are wholly superfluous. 



But the most elaborate and philosophical attempt to place 

 the classification of these forms on a more natural basis has 

 been made by Prof. Smitt in his ' Critical Review of the 

 Scandinavian Marine Bryozoa.' 



Every student of the Polyzoa is deeply indebted to the 

 Swedish zoologist for his minute and thorough and discrimi- 

 nating investigation of the northern species, in all the stages 

 of their growth and development, and through all their varie- 

 tal modifications, and, whether he may accept all his con- 

 clusions or not, for his suggestive views respecting the true 

 method of classification. Whilst freely admitting the great 

 value of those views under many of their aspects, 1 find 

 myself quite unable to accept a large number of the practical 

 results to which they have conducted their author. 



In attempting the very difficult task of revising the classifi- 

 cation of the Membraniporidce^ I have derived the most valu- 

 able assistance from Prof. Smitt's writings ; but I have been 

 compelled to differ frequently from him as to the definition 

 and composition of the groups which arc to supplant the 

 older divisions. In the present paper I merely propose to 

 characterize briefly some of the new genera into which, I 

 believe, the Memhranipora and Lepralia of authors ought to 

 be resolved. 



The genus Lepralia includes a multitude of forms agreeing 



