Natural History of East Finmarh. 593 



fiof. 10). The length of a zooecium is about 08 millim., 

 while that of C. unicornis is 0'6 millim. ; but there is con- 

 siderable variation in the size of both forms. 



E. unicorms, var. armifera, is in my collection from the 

 following localities: — Spitsbergen (Smitt as '' Membranipora 

 vnicornis") : Upper Torske Bank, W. Greenland (' Valorous/ 

 1875) ; Gulf of St. Lawrence [Whiteaves) ; Nantucket, N.E. 

 America (received among some unnamed specimens from 

 Prof. Verrill). 



One difficulty presented to us in studying the Polvzoa 

 is the circumstance that all the zooecia in a polyzoary imitate 

 any marked peculiarity of varietal characters which is 

 developed on the earliest zooecia ; and thus, without a series 

 of specimens to show the connecting-links, such a specimen 

 may be regarded as possessing more permanent characters 

 than it is entitled to : the two forms of this species on the 

 Pecten from the Torske Bank are a case in point, which 

 might be multiplied endlessly. Even if the earliest zooecia 

 are of smaller or larger size than usual, the whole colony 

 will follow suit and maintain that dimension. I have made 

 some observations on this subject in my paper " A Month 

 on the Trondhjem Fiord/'' when treating of Electra pHosa 

 (Ann. & Mag. Nat. Hist. ser. G, vol. xiii. 1893, pp. 121, 12.2). 



Callopora nigrans, Hincks. (Figs. 1, 2.) * 



F 1851. ReptoJIustrella americana, d'Orbij,^}^, Palteout. Franc, Terr. 



Cret. vol. V. p. 571. 

 18(i7. Membranipora lineata, forma americana, Smitt, '' Kiitisk Fiir- 



teckning, &c." p. -366 {partiin, nccjhjurcc). 

 1882. Memljranipora nu/rans, Ilincks, " Polvzoa Charlotte Islands," 



Ann. & Mag. Nat. Hist. ser. o, vol. x. p. U (separate copy), pi. xix. 



ti^. 2. 

 1900. Memhranipora macilenta, Waters, " Cryozoa Franz-Josef Land," 



Journ. Linn. Soc, Zooi. vol. xxxviii. p. 01, pi. viii. tig-. 10. 



Zooecia very large, commonly 0'8 and 0"9 millim., ovate 

 (oblong or linguiform when crowded), margin crenated ; 

 oral opening large, semicircular; a lateral avicularium is 

 soon developed high up on each side, with acute mandible 

 pointing obliquely downwards. The zooecium is now in the 

 condition in which it is represented by Waters and my fig. lb. 

 Next, above the zooecium is produced a transversely oblong 

 fillet, the margins of which are slightly raised, so that there 

 is a slight hollow on the middle portion, and the distal 

 corners are rounded off (see fig. 2 a). Next, upon the 



* Plo-ures of this .•-pecics will be given witli the next part ; those here 

 mentioned refer to them. 



