70 Bev. T. Hincks's Contributions towards 



means my intention, however, to confine myself to bare 

 diagnosis. The following points especially may, I hope, 

 receive some elucidation : — (1) geographical distribution — 

 any new localities for known species will be recorded ; (2) 

 local variation — the differences exhibited by the same type 

 under differing circumstances will be noted whenever the 

 opportunity presents itself of comparing specimens of the 

 same species from various parts of the world ; (3) the limits 

 of variability in each case, and the elements of structure most 

 liable to variation ; (4) the true principles of classification. 

 With the descriptions of new forms will be combined notes on 

 such as are little known or misunderstood ; and, so far as the 

 space at my command will permit, I shall endeavour to indi- 

 cate in the case of each genus the number of species already 

 ranked under it, and its geographical range. If I should be 

 able to carry out with any completeness this portion of my 

 programme, these papers will serve as an index to the foreign 

 species which have already been described, as well as an 

 introduction to many that are new. 



The classification employed will be that which I have 

 adopted in my ' History of the British Marine Polyzoa,' so 

 far as it applies, and with such modification as may be sug- 

 gested by an increased knowledge of the morphology of the 

 tribe. 



At the close of the series of papers a bibliographical list 

 will be given, containing the principal faunistic and other 

 w.orks which deal with the foreign species of Polyzoa. 



I shall commence with an account of a very interesting 

 series of specimens from Madeira, for which I am indebted to 

 Mr. J. Y. Johnson, who is so well known as an investigator 

 of the fauna of that island. 



I. MADEIRAN POLYZOA. 



Subclass Holobranchia, Lankester. 



Group Ectoprocta, Nitsche. 



Order GYMNOLiEMATA, Allman. 



Suborder Cheilostomata, Busk. 



Family Membraniporidae. 



Membranipora, Blainville. 



Membranipora tenuirostris, n. sp. (PI. IX. fig. 3.) 



Membranipora Fleminyii, Waters, Bryoz. Bav of Naples, Ann. Feb. 

 1879, p. 122, pi. xiii. fig. 2. 



Zooecia oval, or broad below and narrowed above (rather 



