Zoological Society. !^95 



PROCEEDINGS OF LEARNED SOCIETIES. 



ZOOLOGICAL SOCIETY. 



November 24, 1857.— John Gould, Esq., F.R.S., V.P., in the Chair. 



Observations on the genus Furcella, Oken, a Con- 

 chifer without concha or normal valves, and on the 

 GENERA Teredo and Ch^na. By John Edward Gray, 

 Ph.D., F.R.S., V.P.Z.S. etc. 



The shelly tube of this animal has been described under several 

 names. Linnaeus considered it as a Serpula ; Pallas, Home, and 

 more recently Messrs. Adams have regarded it as a Teredo. Oken 

 (1815) considered it a genus under the name oi Furcella, to which 

 the following names have been given: — Septaria, Lamk., Closso- 

 naria, Ferussac, Clausaria, Menke, Kuphus, Gray, altered to Kyphus 

 by Agassiz. 



There is no doubt that it is allied to Teredo, and it has been se- 

 parated from that genus by the older conchologists because the apex 

 of the tube is solid and furnished with two separate tubular aper- 

 tures, evidently for the siphons of the animal, which in some speci- 

 mens are said to be produced beyond the end of the larger tube 

 into two slender, elongated, cylindrical tubules, as figured by Rum- 

 phius ; hence the name given to it by Oken : but I have never 

 seen a specimen which exhibited this character. 



The habit of the animal at once separates it from Teredo, which 

 always lives in wood, while the Furcella lives sunk perpendicularly 

 in the sandy mud of the tropical seas. 



The external appearance of the shelly tube agrees with this ha- 

 bitat ; for instead of being nearly cylindrical and more or less twisted 

 according to the hardness or knots in the wood, it is club-shaped 

 and closed at the larger end with a convex plate like the tube of 

 Chcena mumia, which lives in the sand in a similar manner ; but 

 the tube of the Furcella is much larger, and generally rather distorted 

 and irregular on the surface, divided into sections by more or less 

 distinct constriction of its diameter or by the shght alteration in the 

 direction of the tube, which on examination are evidently produced 

 by the periodical stoppages in the growth of the animal, which 

 at each period of suspended activity evidently closes up the end of 

 the tube; the animal absorbs this terminal plate when it again 

 returns to activity, and requires a larger tube for its increasing 

 dimensions. In the specimen before me, the space between these in- 

 terruptions in growth increased in length as the animal grew and 

 enlarged in diameter. 



The tube is thickened above as the animal leaves it, and is much 

 thinner near the lower or closed extremity. The whole length of 

 the tube is solid, without any perforations, except quite near the 

 closed end, where it is pierced with a number of unequal-sized rather 

 irregularly disposed small perforations, generally scattered ; but some- 

 times there is a short series of five or six placed in a longitudinal 



