MARSHALL: ADDITIONS TO “ BRITISH CONCHOLOGY.” 349 
possible for S. eddystonta to be something else, for I am 
not infallible, let it be demonstrated in an_ intelligible 
manner; it is not sufficient to string together the above 
inaccuracies and add “I have been able to satisfy myself 
about it.” 
Montacuta substriata Mont.—-Low water to go fathoms. 
Channel and Scilly Islands, at low water of spring tides, on 
Spatangus furpureus ; the former are very fine—r¥ lines by 
ti. From two to six specimens occur on an individual 
Spatangus. Jeffreys gives a good figure, but erroneously 
shows the riblets as bifurcating, instead of radiating straight 
from the beaks. Sowerby’s is not like our shell in shape, 
sculpture, or colour. 
Var. leevis Jeff.rDoggerbank, 35 f. 
M. bidentata Mont.—-Low water of spring tides to 70 fathoms. 
Under stones at Guernsey, of a large size—-2 lines by 14. 
Var. triangularis Jeff.—Torbay ; Milford Haven ; Skye ; 
Aberdeen ; Dornoch Frith ; W. Orkneys, 45 f. ; Shetlands. 
It is rare. 
M. tumidula Jeff—-This species lives in muddy sand through- 
out the Hebrides, in 18—g5 f., but is everywhere rare. 
The following localities and depths I can vouch for :—Off 
ochranzas ssi) um lisland se aieys) Soundion ssleat, 
40—95 f. ; and Skelmorlie, 18 f. ; (Somerville and J.T.M.) ; 
between Jona and Staffa, 38 f.; off Tarbert, 25 f.; off Arran, 
25 f.; Loch Fyne, 45—56 f. ; Loch Linnhe, 2o—30 f. ; 
Loch Hourn, 25 f.; the Minch, ro—4o f.; also in the 
Atlantic off Scilly, 690 f., two valves (‘ Porcupine’) ! 
The posterior ends of all my specimens are not so 
“extremely short and abruptly sloping downwards” as 
Jeffreys’ figure, but are sloping outwards and rounded off, 
exactly as in Zapes virgineus of the same size. Perhaps 
Jeffreys’ figure was taken from a Norwegian specimen, as I 
have it from Drobak exactly as pourtrayed in “ British 
