102 THE VOYAGE OF H.M.S. CHALLENGER. 



in p;n't, quite regularly formed with six long, smooth, conical rays, and in part more 

 irregularly with bent and knotted rays. Wy ville Thomson describes as peculiar " flesh 

 spicules " the small regular hexradiate forms which cover the skeletal framework and are 

 abundantly scattered throughout the soft parts, and also the elegant structures which 

 were termed " floricomo-hexradiate stellate" by Bowerbank, in which each of the six 

 principal rays is continued into a small, outwardly curved, richly pronged, terminal plate, 

 and into a petaloid system of small branches which are bent in an S-shaped manner, and 

 widened at their extremities. The network of fibres forming the terminal sieve-plate, 

 which extends all round the sharply truncated lip-like upper walls of the tube, consists of 

 the very same elements as the wall of the tulie, but appears more closely woven, and 

 exhibits large six-rayed spicules between the rod-like forms, which are in general some- 

 what short. Besides this completely preserved skeleton, which has been figured by 

 Wyville Thomson from a photograph, the JMuseum of the Jardin des Plantes in Paris is 

 said to contain a second injured specimen and a fragment of a third. 



As to the other form, designated by Gray Corhitella speciosa — Habrodictyum 

 speciosum, Quoy and Gaimard — Wyville Thomson was able to study only the single 

 specimen contained in the Museum of the Jardin des Plantes, and labelled ' Alcyon- 

 cellum corhicula Val. tir^ par 80 brasses de profondeur dans la rade de St. Denis de 

 Bourbon par M. Leschenault 1819." This is probably identical with the specimen 

 first described and figured as Alcyoncellum speciosxim by Quoy and Gaimard in their 

 great work. It exhibits a lattice-like tube 19 cm. long, which gradually widens from a 

 base which, when fully grown, is 32 mm. broad, to a free upper extremity which is 

 60 mm. in breadth. The lateral wall of the tube does not, as in HeteroteUa corhicula, 

 end in a sharply truncated upper margin, nor become closed by a flat transverse sieve- 

 plate, but, without changing in texture, bends inwards, and so forms a curved arch 

 which serves to close the tube above. While the rod and spindle-like spicules which 

 compose the lattice-like framework, and also the larger six-rayed sj^icules, resemble the 

 corresponding elements of the other species except in a few differences in size, and while 

 both the above-mentioned small, stellate six-rayed forms and "floricomo-hexradiate 

 stellate spicules " recur in similar form and size scattered through the soft body, there is 

 further a very abundant occurrence of a flesh spicule, which has not been certainly observed 

 in Habrodictyum corbicida, namely, a small hexradiate form with its branches divided 

 longitudinally in a forked or trifid manner. It was the great abundance of this form, 

 which Bowerbank tenned a " bifurcate rectangulated hexradiate spicule," which mainly 

 induced Wyville Thomson to regard Habrodictyum speciosum, Quoy and Gaimard, in every 



' The circumstance already recorded by Gray (Ann. and Mag. Nat. Hist., ser. 4, vol. i. p. 173) is striking, and one 

 by no means easy to reconcile with the above supposition, namely, that in the Voyage de 1' Astrolabe Quoy and Gaimard 

 note that their specimen was presented to them by Mr. Merkus, governor of the Moluccas. In order to reconcile the 

 two statements it must be accepted that the elegant form which Mr. ilerkus presented did not come from the Moluccas, 

 but from the Isle of Bourbon. 



