NEPTUNEA CONTRARIA. 157 



These two groups occupy at the present time distinct areas, which hardly over- 

 hap. Specimens of the sinistral N. sinistrorsa are recoi-ded from the Mediterranean 

 by Dr. Cams and Prof. Meli, and from Vigo Bay on the Atlantic coast of Spain, 

 where McAndrew found them in some abundance, but they are not known now to 

 the north of the latter locality. 



The dextral N. antiqiui, on the contrary, is characteristically boreal, ranging 

 from British seas northwards to the Norwegian coast, and occasionally to the 

 south of our shores, while the other dextral forms, N. despecta and its varieties, 

 are even more decidedly northern, reaching from the Lofoten Islands to Vadso, 

 and further north in Arctic regions from the Siberian coast to Greenland. The 

 North American shells, Fasus toriiatus and F. decemcostatuH, as well as the 

 Japanese Chrysodomus intersculptus of Gr. B. Sowerby, are closely allied forms. 



Referring to their former distribution, we find none but sinistral Neptuneas 

 occurring as fossils in the south of Europe. They are found in the Pleistocene 

 beds of Sicily, as at Ficarazzi near Palermo, and Reggio in Calabria. On the 

 other hand, the dextral forms which occur in the later Pliocene and Pleistocene of 

 northern Europe are unknown from any such deposits to the south of Great 

 Britain. 



Jeffreys considered the Crag N'. contraria to be a monstrous variety of 

 N. antiqua,^ as did Forbes. It is true that reversed specimens of the latter are 

 occasionally met with living in British seas, but they are hardly the same as the 

 Crag fossils ; except that they are left-handed, they cannot be distinguished from 

 the right-handed shells with which they are found. 



The recent N. sinistrorsa of Vigo Bay, on the contrary, differs materially from 

 both N. ant! qua and N. despecta, corresponding more closely with the Pliocene 

 JV. contraria.'^ 



Deshayes regarded N. coidruria of the English and Belgian Crag as specifically 

 distinct from N. sinistrorsa of the south of Europe, whether Recent or fossil, a view 

 subsequently taken by others. Some authorities, however, while admitting certain 

 differences between the two, prefer to unite them. With this I agree, adopting 

 for the southern and Recent shell the name N. contraria, var. sinistrorsa. 



Belgian specimens of the Scaldisien A. contraria (PI. XVI, fig. 2) occurring in 

 deposits approximately equivalent to the Walton horizon of the English Crag, 

 agree with the English fossils, but being less water- worn show more clearly the 

 characteristic spiral sculpture of this species. 



The arrival of this sinistral form in the Anglo-Belgian basin preceded that of 

 the dextral Neptuneas. It appears first and in the greatest profusion at Walton-on- 

 Naze, the earliest of the Waltonian deposits, the dextral shells establishing tliem- 



' Brit. Couch., vol. iv, p. 325, 1867. 



- See Proc. Internat. Congress Zool. (Cambridge), p. 223, pi. iii, 1898. 



