324 



ADDITIONS TO "BRITISH CONCHOLOGY." 



By f. T. MARSHALL. 



Part VII. (continued from page Jo6). 



P],ATE 5. 



P. tlirricula Mont. — Herm beach (Tomlin). Mr. Tomlin's Herni 

 record, cited by Mr. Marquand,^ requires confirmation. I do not 

 think this species, common though it is, occurs in any of the (Channel 

 Islands, although Mr. Tomlin "certainly found an unmistakable/*. 

 tlirricula on the shell-beach " at Herm. 



van rosea M. Sars. — Connemara (Tomlin and Dodd) ! Aberdeen- 

 shire (Simpson) ! Uoggerbank, Belfast Lough, and Loch Linnhe. 

 This variety is Tritoniuni roseuni of M. Sars, and no more than a 

 tinted form of the type. 



var. ecostata Norman.- — Dublin Bay (Walpole fide Norman). 

 Found occasionally with the type, though at Portrush and Port- 

 stewart it forms 25 per cent, of the specimens. In this variety the 

 longitudinal ribs are more or less absent. 



P. tlirricula is an extremely variable species, either as regards size, 

 degree of sculpture, or proportions of length to breadth. In the Nor- 

 wegian seas especially it seems to reach its highest degree of develop- 

 ment and variation. Doggerbank and Aberdeenshire specimens attain 

 fin. in length. It is usually white, but is sometimes lemon-coloured 

 (especially from the west of Ireland), and more rarely tinged with 

 pink. A small and stumpy form from the Kyles of Bute, in i8f., has 

 the proportions of P. exarata Moll. The latter species was dredged 

 by the ' Porcupine' in the Atlantic off Ireland in i64-i23of. (Jeffreys), 

 and by the Scottish Fishery Board in the Minch in 63f., and off the 

 Butt of Lewis in 545f. (Simpson) ! 



P. trevelyana Turt. — Brora, from haddocks (Baillie) ! St. 

 Andrew's, from fish stomachs (M'Intosh) ; Scarborough, Filey, and 

 Whitby, sometimes cast ashore; Frith of Lome 75f.; Dornoch Frith, 



Individual specimens of this and the last species approach each 

 other closely in shape and size, shouldering whorls, and longitudinal 

 ribs ; but the sculpture of this is always finer, while the aperture is 

 shorter and the canal more open. The longitudinal ribs vary in 

 number and size, and are sometimes altogether absent, the shell being 

 then evenly decussated, while the young of this form have a 

 considerable resemblance not only to P. ovalis Friele=/'. exigua 



1 Marine Shells of Guernsey, Trans. Guernsey 3oc. Nat. Sci., 1901, p. 16, sep. copy. 



2 Ann. Mag. N. Hist., 1899, vol. iv., p. 133. 



