456 Prof. Reid on the Vogmarus Islandicus. 



colonies. These are startling facts, and go far to disprove Mr. 

 Alder's doctrine, that the tube-like fold of the mantle is for the 

 entry and regulation of branchial currents, which, even if they 

 occasionally occur from spring tides and other causes, can only 

 be in action for a very short time during the twenty-four hours. 

 But I believe that in certain localities these creatures are not 

 immersed in the sea-water for months together during the calms 

 of summer. Many individuals of course inhabit lower levels, 

 and will be more or less submerged. 



Kellia rubra, then, may almost be considered a terrestrial 

 bivalve. When it detaches itself from its hyaline delicate fila- 

 mentary byssus, as it frequently does, to change place, food, and 

 remove into more humid quarters, it is unable by its long slendej 

 foot to drag itself over the interstices of the fuci and the aspe- 

 rities or other matters in which it may happen to be settled 

 without the aid of an additional power, which I am inclined to 

 think is furnished by the extended fold of the mantle ; and this 

 supposition appears to receive strong support by the isochronal 

 action of the foot and fold. 



I am. Gentlemen, your most obedient servant, 



William Clark. 



XLVII. — An Account of a Specimen of the Vaagmaer, or Vog- 

 marus Islandicus (Trachypterus Bogmarus of Cuvier and Va- 

 lenciennes), thrown ashore in the Firth of Forth. By John 

 Reid, M.D., Professor of Anatomy and Medicine in the Uni- 

 versity of St. Andrews. 



[With a Plate.] 



This fish was sent me on the 7th of April 1848 by Dr. John 

 Berwick of Elie, near which place it was cast ashore dead. It 

 was perfectly fresh when I received it ; but the dorsal and caudal 

 fins were damaged, and the ventral fins were entirely wanting — 

 a condition, which, from the brittleness of these parts, is gene- 

 rally found in the adults of this genus of fishes*. Its characters 

 showed distinctly that it belonged to the family Tsenioides and 

 genus Trachyptm'us of Cuvier and Valenciennes, and on compa- 

 ring these with the descriptions of the species of Trachypterus 

 given in the work of Cuvier and Valenciennes, and that of the 

 Trachypterus vogmarus or bogmarus by Professor John Reinhardt 

 of Copenhagen, contained in the Supplement to the 1st edition, 



* Histoire naturelle des Poissons, par Cuvier et Valenciennes, tome x. 

 pp. 314-15, and pp. ;32.'?-26. Paris, 18^5. 



