7 
MARSHALL: ADDITIONS TO “BRITISH CONCHOLOGY.” 351 
I discovered this species near Torquay in 1886, ina 
very limited area of shelly mud at extreme low water, 
obtaining four perfect but dead specimens and as many 
valves. Two of these are in the National Collection. 
Whether living in this habitat or drifted in from the bay, 
it is impossible to say. 
The shell under the epidermis has occasionally a few 
clear-white streaks radiating from the beaks, as in Lefton 
clarkie, and in outward appearance it is very much like a 
young specimen of that shell. It has almost the same out- 
line, the same concentric striz, and sometimes the same 
longitudinal rays ; but the beaks are obtuse and nearer the 
posterior end, it is not so compressed, and it is more 
oblique. Inwardly, the dentition is seen to be different ; 
for such a minute shell it has wonderfully strong and 
prominent teeth. As Lefton clarkie varies very much in 
obliquity, I know of no more certain character to distin- 
guish the two species than the dentition, which cannot be 
mistaken, for while Z. clarki@ has a cardinal tooth under 
each beak, JZ. dawsoni has none, the space being filled up 
with the cartilage when alive. 
All the British specimens I have seen are much eroded 
about the beaks, but those from Davis Straits are only 
slightly so. The latter are four times as large as British 
examples ; they are less oblique, the umbones are more 
tumid, and they have a conspicuous yellowish-brown 
epidermis. ‘The latter form somewhat resembles a young 
Nucula nucleus. Jeffreys has stated’ that Mr. Dawson’s 
specimens ‘‘may be semi-fossil or relics of the glacial 
epoch”, but the additional records I have given above dis- 
pose of that. There is no good figure of this species, 
both Jeffreys’ and Sowerby’s being useful merely as outlines. 
Laseea rubra Mont.— Alderney, in submerged wooden piles. 
x. Ann. and Mag. Nat. Hist., Dec. 1876, ser. 4, vol. 18, pp. 490-1. 
