NATICA. 229 



more open, and furnished with a broad ridge, which is 

 defined on the lower side by a deep groove. 



It is the Nerita rufa of Montagu ; but Born's species 

 of that name (which belongs to the present genus) is a 

 large tropical shell. Macgillivray described our species 

 as Natica rutila, and the young as N. squalida. I have 

 ventured, for the sake of uniformity, to slightly alter 

 the spelling of the specific name given by Forbes. Mon- 

 tagu's ancestor in Domesday Book was Drogo de Monte 

 acuto, afterwards Montacute and Montagu ; the La- 

 tinized form of the name is therefore Montacutus, and 

 not Montaguus. Thus we have the well-known genus 

 Montacuta. 



One of the most common shells in our newer tertiary 

 and quaternary formations is the Nerita affinis of 

 Gmelin, alias Natica clausa of Broderip and Sowerby. 

 I will mention only a few of the localities, to show the 

 extent of oscillation to which the area of the British 

 Isles and of the surrounding sea has been subjected 

 within a comparatively recent period : — Mammalian and 

 Red Crag, not much above the present level of the sea 

 (S.Wood); Moel Tryfaen, 1330-1360 feet (Darbishire); 

 dredged in 25 f. = 150 feet, off Larne, co. Antrim, and 

 from a raised sea-beach near high-water mark, at Fort 

 William (J. G. J.) ; Clyde district, at a considerable 

 height (Watson and others) ; Shetland sea-bed, 80 f. = 

 480 feet (Barlee). It now inhabits the circumpolar and 

 northern ocean in both hemispheres, its southern limit 

 on this side of the Atlantic being Drobak in Christiania- 

 fiord (Sars), with a bathymetrical range from the shore 

 to 150 f. It occurs in a fossil state throughout Scan- 

 dinavia and Canada; and Dr. Van Geuns discovered it 

 in a pliocene bed near Palermo. I need not particu- 

 larize the synonyms of this species. 



