452 Mr. W. Clark on the Animal of Kellia rubra. 



XL VI. — On the Animal of Kellia rubra. 

 By W. Clark, Esq. 



To the Editors of the Annals of Natural History. 



Gentlemen, Norfolk Crescent, Bath, May 5, 1849. 



I BEG you to allow me the insertion of a few observations, in 

 reply to Mr. Alder's last paper on Kellia rubra in the May num- 

 ber of the ' Annals.' 



That gentleman has stated the result of his re-examination of 

 the animal of Kellia ruhra with great candour, observing that 

 "in all cases" I have described "the parts very correctly .'' I 

 feel pleasure in the corroboration of my examination of this very 

 minute bivalve by so competent an observer, though we differ as 

 to their uses. But however far apart our opinions may be, we 

 will not forget in our disputations the prayer of the nymph 

 Arethusa, — 



" Doris amara suam non intermisceat undam." 



I do not think it will be difficult to show that the anterior 

 tube-like fold of the mantle of Kellia rubra is not a special 

 branchial organ, according to Mr. Alder's views, and which he 

 still retains. 



It must be borne in mind that the mantle of Kellia rubra is 

 open from the posterior branchial slit to its anterior termination. 

 The open fold in question is merely a prolongation of that mem- 

 brane ; and when the animal opens its valves, it must receive, 

 like the Mactrce and Veneres, or any other bivalve with an open 

 mantle, the currents of sea-water ; and in closing them, a great 

 part thereof, after bathing the branchiae, is ejected from the 

 aperture of ingress, and only a portion of it passes out by the 

 posterior orifices. 



These remarks will show that I did not use the words 

 " branchial and anal, as applied to these apertures, in a literal 

 and restricted sense." I am not aware I have said anything to 

 warrant this inference. Mr. Alder has misunderstood me. I 

 only stated that the posterior branchial slit in Kellia rubra is 

 both a receiver and expeller of water ; and this view I firmly ad- 

 here to. I never intended to state it was the only one, when 

 the contrary fact is so evident in Kellia rubra. 



Mr. Alder observes, that, agreeably to the " known oeconomy 

 of the bivalves, the inhalant is always kept distinct from the ex- 

 halant current, and admitted by a separate aperture from that 

 by which the latter is expelled." This position is, I think, incor- 

 rect ; as in those bivalves with open mantles the currents of 

 water enter by the great pedal orifice or I'ima magna of the 

 mantle, to aerate the branchiae, and the greater part of the im- 



