1881.] THE SURVEY OF H.M.S. ' ALERT.' 107 



latter reason they are with difficulty distinguishable with a lens in 

 this position, though the naked eye is sufficient to make them out 

 in L. antarctica ; the bareness ot" the stem and of the greater portion 

 of the chief branches is perhaps the most striking superficial point of 

 difference. 



The species is dedicated to Mr. H. N. Moseley, to whom we owe 

 so much for conclusively determining the affinities of the group to 

 which it belongs. It seems in some respects to connect Errina with 

 Labiopora, representing a trfinsition from the strongly to the feeWy 

 labiate character of the chief dacty lopores. The comparative absence 

 of prominent dactylopores from the anterior and posterior surfaces 

 of the frond would be an important character, were it not that both 

 this and the condition iu which they are universally distributed are 

 found in Errinam the Museum collection. The colour, too, cannot 

 be appealed to, considering the variations which are shown in this 

 respect by the kindred genus Stxjlaster and (if E. fissurata. Gray is 

 an Errina, and if the figure by which we know it was taken from 

 a macerated specimen) by Errina itself. 



XI. SPONGIDA. 



By Stuart O. Ridley. 



(Plates X., XI.) 



Horny and Siliceous Sponges of Magellan Straits, S. W. Chili, and 

 Atlantic off S.W. Brazil. 



With regard to the technical nomenclature of the different parts of 

 the Sponges here described, the terms employed are used with the 

 meanings which they bear in Mr. Carter's writings '. In measuring 

 the spicules with the view of stating the typical form and size, the 

 object has been to determine the average largest size of each de- 

 scribed form ; in each case at least Jive of the largest of each form 

 were picked out and measured in order to decide this point. The 

 diameter given for a spicule is the greatest diameter iu each case, 

 except that of spinulates or similar forms, where the diameter given 

 is that of the body, not of the head ; in the case of spined spicules 

 the base alone of the spines is included in the measurements. 



Considerable details have been given under many of the species 

 with regard to the structure of allied forms elsewhere described 

 (chiefly by Bowerbank, Schmidt, and Lamarck). It should be ob- 

 served that these details are obtained from a fresh and independent 

 study (1) of actual type specimens or slides as far as these could be 

 fixed, in the case of the Bowerbankian species ; (2) of the shdes 

 and specimens furnished to the Museum by Prof. Schmidt himself, 

 in the case of the species described by him ; (3) of a collection 

 which undoubtedly represents the type specimens, in the case of 

 Lamarckian species. The type specimen oi Ciocahjpta tuberculata. 

 Carter (see infra), has also been carefully examined. In all these 



' Cf. especially his " Notes Introductory to the Study " &c., Ann. N. H. 

 (4) xvi. pp. 1-40, 126-145, 177-200. 



