BELA TURRICULA. 277 



forms described by Scandinavian geologists, which, with the exception of B. 

 Trevelyana, are unknown in British seas. 



When "Wood's Monograph was written in 1848 — 50, the Arctic Belas were but 

 little known in this country. Authors like Moller did not figure, and but 

 imperfectly described the various forms noticed for the first time in their 

 writings, and regarded by them as specifically distinct. Wood had, therefore, no 

 alternative but to group the few specimens of Bela which came under his notice as 

 B. turricnla. 



Jeffreys, moreover, as late as 1867, adopted a similar view, and much confusion 

 has arisen in consequence. When the latter says, for example (op. cif., p. 397), 

 that B. iurncula occurs in Greenland or Spitzbergen, he creates a wrong 

 impression ; he is really referring to Scandinavian and Arctic forms like B. nohilu, 

 B. scalaris, or B. exarata, which in the context he associates with it. To this 

 day, unfortunately, the confusion continues ; many such Crag Belas may be still 

 found in our museums and in private collections under the former name, and 

 lists of Crag Mollusca often contain the name of B. turricnla ; but such lists 

 cannot be relied on. 



It should be noted, however, that Prof. Kobelt, and more recently MM. 

 Dautzenberg and H. Fischer, have proposed to regard many of the northern Belas 

 referred to in the sequel as varieties of B. turricnla ; but with all the respect due to 

 such authorities, I doubt whether this is desirable.^ The most of them are now^ 

 characteristic denizens of polar seas, ranging but little to the south of the Arctic 

 circle. On the other hand, there is no evidence to show that the typical B. 

 turricula was in existence in the North Sea at the beginning of the Red Crag 

 period. I have not met with it at Oakley, and, as far as I know, it is exceed- 

 ingly rare at later horizons of the Crag, though it occurs occasionally in the Manx 

 beds and in the Wexford gravels. As a characteristic form, however it belongs to 

 the Pleistocene rather than to the Pliocene deposits, being apparently one of the 

 latest of the Belas to establish itself in any abundance in the Crag basin. 



After all, nomenclature is to a great extent a matter of convenience. We no 

 longer think, as in pre-Darwinian days, that species are separated by an impassable 

 barrier, each having had its specially created progenitor. It appears rather 

 absurd to a geologist, though perhaps not to a zoologist, to place what seems to 

 have been a comparatively recently developed form in loco parentis to a group 

 of species which were probably numerous and wide-spread long before their 

 suggested ancestor or prototype had come into existence, especially as many 

 of these well-marked northern forms show a continuity of existence from Waltonian 

 times to the present day. 



Mr. Friele takes a somewhat similar view. Protesting against the grouping 



1 I cannot regard Prof. Kobelt's figure of B. turricula {op. cit., vol. iii, pi. lxxxii,fig. 1) as typical 

 of the Recent British shell; indeed, he identifies it with B. rugulata. 



