Dr. J. E. Gray on the genus FurccUa. 375 



loped, shelly valves, and also as the homologue of the shelly valves 

 in the genus of the family which is without true valves. 



Hence I must continue to regard Furcella as a Conchifer with- 

 out shelly valves, or any part homologous to them ; and if we were 

 to find a Conchifer without valves, I should consider their absence 

 would be most likely to occur in a family in which the valves of 

 the normal members are so reduced in comparison with the size 

 of the animal as in TeredinidcB, where they have been regarded as 

 " mere appendages of the foot ;" this also being a family of Bivalve 

 MoUusca, in which the animals always live in a shelly tube, it is one 

 in which the valves are least required for their protection. 



Since I sent in the former paper, I have had the opportunity of 

 examining Mr. Cuming's series of Furcella from the Island of Ca- 

 miguen, one of the Philippines, where they live in hard mud left 

 exposed at very low water. 



Mr. Cuming has several specimens of the tube of the vouug ani- 

 mal, which commence with a much smaller diameter than the spe- 

 cimen previously described, and enlarge more rapidly in thickness, 

 so that the tube is more conical. He has two examples of the base 

 of the tube of larger specimens, which end iu the cap formed of two 

 overlapping arched plates, showing that to be the normal formation 

 of the termination. All the specimens have two separate apical 

 siphonal tubes. 



He has also two specimens of the upper part of the tube, which 

 are of a slender, elongated, nearly cylindrical form ; both are pierced 

 through the whole length by two central semicyhndrical tubes, sepa- 

 rated by a narrow opake septum. One of these specimens is water- 

 worn, the other as fresh as if it had been broken from a liA-ing spe- 

 cimen ; the latter shows at the fracture that the apex of the tube is 

 formed of a number of concentric laminae deposited one within the 

 other. The two semicyhndrical siphon-tubes are surrounded with 

 a special opake shelly lamina, the septum between them being of the 

 same thickness and structure ; and between the outer surface of this 

 tube of the siphon and the inner surface of the cylindrical outer 

 sheath or tube, there is a transverse space at each end of the central 

 septum, between the two siphonal tubes, filled with a deposit of a 

 loose, spongy, cellular, shelly texture. 



Mr. Cuming has two small tubes from California which appear to 

 belong to the genus Teredo, and which have the lower or larger end of 

 the tube closed with a single hemispherical cap like those described 

 in my former paper. In one the cap is simple and terminal, and the 

 apex of the tube is oblong and quite simple ; in the other the cap at 

 the lower end of the tube is larger, rather distorted, and bent on one 

 side of the axis of the tube, and the aperture at the apex of the 

 tube is partially divided by a series of plates, which have a promi- 

 nence in the middle on each side, forming an imperfect division of 

 the cavity. 



I may add, that the siphonal end of the tube being divided into 



