BRITISH SPONGIAD^. 365 



specific characters given above are necessarily very imper- 

 fect; yet a sufficient structural difference exists between 

 them and the other British species of Chalina to render 

 their identification by no means difficult. The only British 

 species with which C. cervicornis is liable to be confounded 

 is with slender specimens of C. oculata, and Dr. Johnston 

 states, in page 97 of his ' History of British Sponges/ that 

 "Dr. Fleming considers Halichondria cervicornis to be a 

 variety of H. oculata, and I have seen specimens which 

 favour this opinion, but in general their distinction is easy 

 enough. The spicula are alike in both." With the first 

 sentence ia this quotation I perfectly agree, but not so with 

 the second, as although the forms of the spicula in the two 

 species compared are both acerate, their proportions are 

 widely different ; those of C. oculata being more than twice 

 the length of those of C cervicornis, in fact, as seventeen to 

 seven ; so that however similar worn specimens of either 

 species may be to each other, the relative proportions of 

 their spicula afford a ready means of discrimination. Dr. 

 Johnston, in plate iv of his ' History of British Sponges,' 

 has figured, apparently,, a short and somewhat digitate 

 specimen of Chalina oculata, " from a specimen in the col- 

 lection of the late Mr. Templeton," as the magnified figure 

 agrees with the structure of that species. Dr. Johnston 

 also includes in his synonyms Sponffia ramosa of Gerhard's 

 Herbal, emended 1577, No. 9, and Spongia stuposa, Ellis 

 and Solander's Zoophytes, 186, but both of these species 

 undoubtedly belong to a different genus, and are described 

 among our British species of Dictyocylindrus, as D. ramosa 

 and D. stwposa. Montagu's Spongia digitata is also con- 

 sidered as a synonym of Halichondria cervicornis of John- 

 ston, and this also is a misconception. I have had the 

 advantage of examining Montagu's type specimen of his 

 species, now in the possession of Professor Grant, of 

 University College, and the result is, that it is not a sponge, 

 but an Alga. The species must therefore be considered as 

 those only which agree in their organisation with the types 

 preserved in the British Museum, and represented in Plate v, 

 figs. 1 and 2, in the ' History of British Sponges.' 



