56 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 14, 



greatly. Many are stated to consist solely of a horny network*, 

 but the detection by Mr. Bowerbank of siliceous spicula in corneous 

 sponges t renders doubtful to what extent horny fibres may occur 

 unaccompanied by earthy secretions. M. Milne-Edwards had pre- 

 viously announced the existence in Sp. carbonaria of a " reseau corne 

 herisse de petits spicules siliceux ;" and in the Alcyonium papillosum 

 of Lamarck, of a corneous network with calcareous spicula J. Similar 

 bodies had long claimed attention § ; but their true nature was appa- 

 rently not understood until Dr. Grant investigated the characters of 

 the sponges of the Frith of Forth and other coasts || . In one great 

 tribe he announced that *' the axis is entirely calcareous, and soluble 

 with eifervescence in acids " {op. cit. vol. xiv. p. 336), and that in 

 very many others " the fibres are composed of minute siliceous tubes" 

 (p. 337). In addition, however, to these decidedly mineral struc- 

 tures, M. Milne-Edwards has shown that earthy constituents are 

 combined in sponges in many other states : m Sp. penicillosa, the 

 filaments " renferment dans leur substance un pen de carbonate de 

 chaux^ ;" also in Sp. calyx (p. 556) ; while in Sp.pennatula " ces 

 filaments" come " sont solidifies par du carbonate de chaux. Par- 

 enchyme herisse de petits spicules siliceux" (p. 560-561) ; and Sp. 

 juniperina, he says, is composed of " un reseau come, dont les fila- 

 mens s'elargissent beaucoup dans leurs points de soudure, et sont en- 

 toures d'une multitude de petits spicules de silice et de quelqucs 

 granulations calcaires" (p. 563-4) ; lastly, for the Sp. fragilis of 

 Montagu**, Dr. Johnston has founded on his own and Mr. Bower- 

 bank's observations the genus Dyseideaff, in consequence of the 

 grains of sand, which Montagu had also noticed. The compiler of 

 this notice is not aware whether the species just mentioned have 

 been recently arranged under distinct names ; but it is well known 

 that Dr. Fleming;;]; J proposed the terms Halichondria and Grantia 

 for sponges respectively composed of siliceous or calcareous spicula 

 {op. cit. pp. 520, 524), while he retained the word Spongia for the 

 species which have a decidedly corneous framework. These '* ge- 

 nera," however, have been regarded by Dr. Grant as " orders §§," and 



* Consult Lamarck, 2nd Ed. vol. ii. p. 543 et seq., nos. 7, 9, 11, 12, 45, 46, 48, 

 54,63, 73, 114. 



t Annals Nat. Hist. vol. vii. p. 129, 1841 ; and Trans. Geol. Soc. 2nd ser. vol. vi. 

 p. 182 note. 



X Lamarck, 2nd Ed. vol. ii. p. 546, No. 20, p. 604-5, No. 23, 1836. 



§ Consult Ellis, Nat. Hist. Corallines, 1754, Sponges, No. 2 ; Ellis and Solander, 

 Zoophytes, 1786, tab. 58. fig. 4, or Lamouroux's Exp. Method, tab. 58. fig. 4 : also 

 Montagu, Essay on British Sponges, Wern. Trans. voL ii. p. 93 et ^eg., particularly 

 pp. 93, 116, 88, 89, 95, 97 and 99. 



II Edin. Phil. Journ. vol. xiii. pp. 94, 333, and vol. xiv. pp. 113, 336, 1825-26. 



% Lamarck, 2nd Ed. tome ii. p. 548 ; consult also p. 540. 



** Wernerian Trans, vol. ii. p. 114. pi. 14. fig- 1, 2. 



ft History of British Sponges, pp. 185, 187-190, pi. 13. fig. 6, pi. 14. fig. 4, 1842. 



X% History of British Animals, 1828. Dr. Grant has proposed Halina and Hali- 

 clona for siliceous sponges, as quoted by Dr. Johnston, op. cit. p. 88, and M. de 

 Blainville, Halispongia, Man. d'Actinologie, p. 532, 1830, 1834 : for Grantia, Dr. 

 Grant has also proposed Leucalia, and Leuconia (apud Dr. Johnston, p. 172), while 

 De Blainville has applied to the same bodies Calcispongia {pp. cit. p. 530). 



§§ Todd's British Annual for 1838, p. 268. 



