1867.] DR. BOWERBANK ON HYALONEMA LUSITANICUM. 903 



piece mounted in its natural state the structure of the skeleton was 

 distinctly exhibited, exactly resembling, in the forms of its component 

 spicula and in the mode of their arrangement, those of the skeleton 

 of the spongeous base of H. mirabile. In the disintegrated portion 

 I found no less than eight forms of spicula which exist in the basal 

 sponge of H. mirabile, and which I have figured in the plates illus- 

 trating my paper on that species (Proc. Zool. Soc. 1867, p. 18). 

 The spicula found were those represented in Plate V. by figures' 2, 

 4, 6, 7, 8, 9, 18, and those of the skeleton. The only difference 

 between the forms of spicula found in Prof. Bocage's specimen and 

 those from H. mirabile is that those of the former are rather more 

 slender in their proportions, indicating a young and not fully deve- 

 loped state of its organization. 



The skeleton-spicula of H. lusitanicum are of about the same 

 length as those of H. mirabile, but somewhat less in their diameter, 

 and they have the same malformations of their apices that so com- 

 monly occur in those of the last-named species. In truth, the spi- 

 cula of H. lusitanicum are so identical in form with those of H. mi- 

 rabile that, without knowing whence they came, it would be impos- 

 sible for an observer to say from which species they had been ob- 

 tained. With these slight differences in the organization of the two 

 specimens under consideration, there is little doubt in my own mind 

 that they belong to one and the same species ; and the slight discre- 

 pancies now apparent in the structure of H. lusitanicum will probably 

 disappear when other perfect and more fully developed specimens 

 are hereafter obtained and compared with H. mirabile ; and in the 

 consideration of these slight differences of structure the influence of 

 their widely separated localities must also be taken into consideration. 

 Another strong argument against H. lusitanicum being a species 

 distinct from H. mirabile is, that no form of spiculum can be de- 

 tected in the spongeous base of the former that is not abundantly 

 present in the corresponding parts of the latter. As regards organic 

 structure, there is no true specific distinction existing between them. 

 Their differences amount only to those of development and such as 

 may naturally arise from variations in climate and locality. 



I have seen the specimen of Hyaloyietna lusitanicum in the British 

 Museum that was presented by Prof. Bocage, through the sides of 

 the glass tube in which it is carefully preserved. It is 2\\ inches 

 long, and has 1 inches of the distal portion of the column covered 

 with corium. The specimen is about 2| lines in diameter. There 

 is the same paucity of sand in the crust that is observable in Mr. 

 Lee's specimen, described by me in the Society's 'Proceedings' 

 (1867, p. 350) ; and, as in that case, each osculum is situated in an 

 elongate-oval area, in which, by the aid of a lens of 2 inches focus, the 

 radiating fibres are readily to be seen. The oscula are none of them 

 elevated to the same extent as in the Japanese specimens, but, like 

 those in Mr. Lee's one, they project very slightly. The oval areas 

 do not all coalesce at their respective boundaries ; in some there is 

 a small space of smooth corium separating them from each other. 

 Having disposed of his new genus Hyalothrix, Dr. Gray proceeds 



