96 



and the opposite ones from six to ten times as long in full- 

 grown specimens : hinge-line very long : ligament broad, sepa- 

 rating the beaks, so as to form a rather wide area : hinge-plate 

 thick, strong, and rounded : teeth consisting of a blunt tubercle 

 in the upper valve, placed a little in front of and below the 

 hinge, and a double tooth in the other valve, into which the 

 tubercular tooth locks: inside highly and beautifully irides- 

 cent, marked with faint and irregular grooves which diverge 

 from the beaks : muscular scars distinct, especially that of the 

 posterior adductor. L. 3. B. 1'65. 



HABITAT : Plymouth offing, procured by the trawlers 

 in 20-25 fathoms, sometimes attached to species of 

 Gorgonia and Sertularia. It is said also to have been 

 found in Dublin and Bantry Bays ; but this wants con- 

 firmation. Dr. Turton's specimen from the first of 

 these localities looks too highly coloured to be British, 

 and is more probably of foreign extraction. The collec- 

 tion of Irish shells made by the late Mr. T. W. Warren, 

 and now in the museum of the Royal Dublin Society, 

 contains a single valve of A. hirundo, which, according 

 to Mr. Warren's Catalogue, was found by him at Port- 

 marnock. This specimen has been kindly sent to me 

 by Dr. Carte, the Superintendent of the museum, for 

 my inspection. Together with it, and on the same 

 tablet, is a young shell of a tropical species of Avicula 

 (or Meleagrina) , which is not unfrequently met with on 

 the bottoms of vessels from South America. The pre- 

 sent species, being in our seas an inhabitant of deep 

 water and always attached, is not likely to be thrown up 

 on a sandy shore. I have never heard of a Pinna being 

 picked up as a similar waif of the ocean. Dr. Carte in- 

 forms me that wrecks too frequently occur in Dublin 

 Bay, which is completely exposed to eastern gales and 

 situate in very nearly the same parallel of latitude as 

 Liverpool, to which port the unfortunate merchant 



