RISSOA. 103 



four fathoms among the Orkneys, and tliat ho has dredgetl 

 it in forty fathoms water between the Orkneys and Fair 

 Island. It ranges from the North Seas to the Mediterranean. 

 The form interrupta does not appear to have so great a 

 range in depth, and is perhaps more abundant in the North 

 than in the South, though common enough everywhere, 

 especially congregating in the Laminarian zone. We have 

 never dredged it deeper than in twelve fathoms water. 



R. cosTULATA, (Risso V) Alder. 



Oblong, conic, strongly ribbed lengthways, and more or less 

 striolate in a spiral direction. Mouth not patulous. Peristome 

 tinged with purple. Labial varix white, not painted with any 

 linear markings. 



Plate LXXVII. fig. 4, 5. 



? Turbo cos{alus, Lam. Anim. s. Vert. (ed. Desh.) vol. ix. p. 219, in part ? 

 Turbo vai-iabilis, M.EG'ERhE Muhlf. Verh. Berlin. Ges. Nat. vol. i. p. 312, in 



part. ? 

 Eissoa costulata, Risso, H. N. Europe Mcr. vol. iv. p. 119, probably. — Alder, 



Ann. Nat. Hist. vol. xiii. p. 324, pi. 8, f. 8, 9. 

 9 „ similis, Scacchi, Catal. p. 14. 2, teste Philippi, Moll. Sicil. vol. ii. p. 124, 



pi. 23, f. 5. 

 ? „ Guerinii, Recluz, Revue Zool. Cuvier. 1843, p. 7. 



The presumed recognition of Risso's species in the 

 present shell rests chiefly on the authority of a specimen 

 marked as such by M. Michaud ; for the identification of 

 Risso's shells is always attended with uncertainty, since 

 that author was neither adequately conversant with the 

 writings of others, nor in the habit of clearly defining the 

 objects he proposed to describe. Hence we look upon 

 our native shell rather as the costidata of Alder, whose 

 description is most admirable, than as accurately corre- 

 sponding to the expressions " epaisse — a neuf tours de 

 spire, punctules de ferrugineux " of Risso, whose language 



