TETHEA. 



87 



Cydonmin of MuUer, Zool. Dan. tab. 81, fig 3, 4, 5, is undoubt- 

 edly nothing but the yellow or orange-coloured variety of AUij- 

 oniuin digitatum. 



The figure of Blainville gives a very erroneous idea of this 

 sponge, and seems to have been drawn from a specimen of a 

 tuberous compact Halichondria, some of which have been ad- 

 mitted into this genus. The Tethi/a lacunata of Lamarck af- 

 fords, as I think, an example of this remark, provided the figure 

 of Schweigger's Beobachtungen, pi. 2. fig. 16, 17, represents 

 that species, though I am aware that Schweigger himself quotes 

 the species as the type of the genus. 



The Alcyonium Bursa of Esper, Alcyon. tab. 8, is appa- 

 rently founded on a dried specimen of the Tethea Lyncurium. 

 I have a portion of a specimen from Torbay in Devonshire, 

 presented to me by Dr Coldstream of Leith, which resembles 

 Esper's figure so closely as to make their specific identity scarce- 

 ly disputable. But the Alcyonium Bursa oi Pallas (Elench. 

 352,) and oi Lamarck (Anim. s. Vert. 2de edit. ii. 608), is now 

 generally acknowledged to be a vegetable production. See Gre- 

 villes Alg. Brit. Inart. 186. 



siliceous balls, precisely as figured and described by Donati in the Alcy- 

 onium primum Dioscordis." — Perhaps two allied species may be here 

 confounded, for the description of Dr Grant seems plainly to be derived 

 from a Tethea. 



Fig. 12. 



TkTHEA LYNLTnU'M. 



