548 PLIOCENE MOLLUSCA. 



tudinal ribs, not very prominent nor soldered together, varying in number, occa- 

 sionally varicose, oblique on the lower whorls, as well as by flattened, closely-set 

 spiral ridges ; spire varying in length, subulate ; suture fairly deep, obscured by 

 the ribs ; mouth ovate, somewhat angulate above ; outer lip strengthened by the 

 last rib ; inner lip thickened at the base ; basal ridge not so strongly marked as in 

 S. similis. 



Dimensions. — L. 30 — 35 mm. B, 10 — 12 mm. 



Distribution. — Ilecent : doubtfully British. Norwegian coast — Christiania fiord 

 to Finmark, Lofoten Islands, Circumpolar — Iceland, Faroe Channel, Spitzbergen, 

 Murman coast, Barentz Sea, Arctic shores of Siljoria, Ijehring Strait, Greenland, 

 eastern and western North America. 



Fossil : Butloyan Crag : Butley. Icenian : Norivich zone, gene- 

 rally diffused. Weyhonrne zone — Belaugh, North Walsham boring, Runton, Wey- 

 bourne. Pleistocene : Middle Glacial — Billockby, Bridlington, Dimlington, Kelsey 

 Hill, King Edward, Clyde beds, Fairlie, Uddevalla, north coast of Russia, 



Remarks. — This characteristically northern and circumpolar form seems to have 

 been one of the latest species of Scala to establish itself in the Crag basin. An 

 occasional specimen has been found at Butley, but I have no note of a verified 

 example of it from earlier horizons of the Red Crag, any which may have been so 

 reported being probably *S^. siinllis, Sowcrl)}?-, to l:)e described in the next paragraph, 

 and this, for reasons there given, I consider should be regarded as specifically 

 distinct. 8. gr(ie)ihi]uUca is, however, a characteristic species of the British 

 Pleistocene. 



It seems to be a species varial:>le in size and in the number of its ribs. At the 

 Jermyn Street Museum, for example, there are two typical specimens from 

 Bridlington, one of them having 14 ribs and measuring 20 mm. by 8 mm., the 

 other is broken, with only 9 ribs, but having been, when perfect, about 80 mm. in 

 length by 12 mm. in breadth. Generally, however, they maintain their distinctive 

 character. 



M. de Boury considered that one of the specimens I have referred to 8. groen- 

 landica (PI. XLVII, fig. 13) resembles more nearly the typical 8. similis. It 

 might be regarded, I think, as a variety of either species. 



Var. crebricostata, G. 0. Sars. Plate XLVII, fig. 1 7. 



1872. Scalaria groenlandica, Dawson, Canadian Nat. [n.s.], vol. vi, p. 394, pi. vi, fig. 11. 



1874. Scalaria groenlandica. Reeve, Concb. Icon., vol. xix, pi. xiv, fig. 107 6. 



1878. Scalaria groitilandica, var. crebricostata, G. O. Sai"s, Moll. Reg. arct. Noi'v., p. 194, pi. xxiii, 



fig. 1. 

 1887. Scalaria groenlandica, Tryon, Man. Conch., vol, ix, pi. xvi, fig. 91. 

 1901. Scalaria groenlandica, var. crebricostata, Friele og Grrieg, Norske Nordhav. Exped., pt. iii 



(MoUusca), p. 79. 



