1888".] ON A WORM OF THE GENUS ^OLOSOMA. 213 



p. 307). The so-called genus Gallocardia, founded upon this species, 

 represented hitherto only by a single valve in the British Museum, 

 and supposed to belong to the family Isocardiidse, certainly belongs 

 to the VeneridBe, and cannot with any propriety be separated from the 

 section Caryatis of the ancient Lamarckian genus Cytherea. This 

 being the case it becomes necessary to change the specific name given 

 to Mr. Adams's type, the name Cytherea guttata being preoccupied 

 by Romer. I therefore propose for it the name of 



Cytherea (Caryatis) isocardia. 



The shell is described by Mr. Edgar A. Smith in his report of the 

 LameUibranchiata of the ' Challenger,' from the before-mentioned 

 single valve. There is little to add to that description. The hinge 

 is almost identical with that of G. hunyerfordl, the shell is more 

 inflated and the umbones more distant. Of the two specimens, 

 one is beautifully painted with squarish hght brown markings, and 

 the other has only angular markings and spots about the dorsal 



EXPLANATION OP PLATE XL 



Fig. 1-3. Cypraa hungerfurdi, p. 208. 



4. Cytherea {Caryatu) hunger- 



forcli, p. 212. 



5. Trochiis ponsonhyi, p. 209. 

 6-7. exquisitus (magnified), 



p. 210. 

 8-9. Columhclla filbyi, p. 208. 



10. Engina. anyulata, p. 210. 



11. Coralliophila turrita, p. 209. 



Fig. 12. Lima smifhi, p. 207. 



13. Helix boxalli, p. 211. 



M. cj/closfremoidcs, p. 212. 



15. Malleka angulata, p. 208. 



l(i. Pleurotoma bulowi, p. 211. 



17. fultoni, p. 210. 



18. Turritella rohusta, p. 211. 



19. Cassis cernica,, p. 211. 



20. Lima concentrica, p. 207. 



3. Observations upon an Annelid of the Genus JEolosoma. 

 By Frank E. Beddard, M.A., F.E.S.E., Prosector to 

 the Society, Lecturer on Biology at Guy's Hospital. 



[Eeceived February 15, 1888.] 



(Plate XII.) 



In looking over a sample of water from a small tank belonging to 

 Mr. Bartlett, Mr. F. W. Headley noted, and directed my attention 

 to, a small worm clinging to a fragment of duckweed. This I 

 recognized as an example of the freshwater Annelid JEolosoma. 

 I obtained further supplies of water from the same tank which was 

 found to be swarming with this little worm. The animals, however, 

 were only rarely observed swimming freely in the clear water, but a 

 large number could be at once brought into view by simply stirring 

 u[) the duckweed with the dipping-tube ; if left to themselves, they 

 rapidly made their way up to the surface of the water where the 

 duckweed was floathig, and disappeared from view. Individuals 



