292 JOURNAL OF CONCHOLOGY, VOL. 9, NO. IO, APRIL, I90O. 



I do not know of any good figure of this species. Jeffreys' is cor- 

 rect in outline, but badly executed, as nearly all his sculptured figures 

 are, and his section showing the specific sculpture is erroneous, being 

 exactly like that of O. interstincta ; Forbes and Hanley's is not good, 

 and Sowerby's is decidedly bad. 



O. interstincta Mont. — I must differ from Dr. Jeffreys in saying 

 that " this species cannot be well mistaken for O. ihdistincta" The 

 two species are as " inconveniently similar " as their names, especially 

 when taken in connection with their varieties. Viewed by types only 

 they are good and well-defined species, but their extreme variability 

 makes the identification of intermediate forms a perplexing task, and 

 they are sure to confuse inexperienced collectors. The principal point of 

 difference from O. indistincta is in the sculpture, which is coarser, with 

 much fewer cross-bars (these cross-bars appearing at the base of the 

 whorls only), and particularly in the presence of a tooth at all stages of 

 growth. Size and shape are of no account whatever as reliable characters. 

 The minor points of difference (and these not always to be relied upon) 

 are the longitudinal ribs, which are twice as broad as their interstices, 

 whereas in O. indistincta they are about equalised ; the last whorl is 

 half the length of the shell, in O. indistincta one-third, and the inter- 

 stitial stria; of the latter appears on the lower half of each whorl, 

 giving a somewhat decussated appearance, especially on the body- 

 whorl. As in the last species, the lower whorls are less compact than 

 the upper, and the longitudinal ribs of the body-whorl, both in the 

 type and all the varieties, are frequently finer and more numerous 

 proportionally. The dimensions given by Jeffreys are not correct, nor 

 in accordance with the proportions of his figure, which I consider to 

 be the true type form ; the breadth should be o - o6 instead of 0*04 in. 

 This type form is rather plentiful in the Channel and Scilly Islands, 

 but scarce elsewhere in Britain, its place being*taken by narrower and 

 varietal forms. 



Var. terebellum Phil. — Milk-white; whorls 8-9; length o - i75 

 in., breadth o - o6. Jersey, Guernsey, and Sark; Torbay; Cawsand Bay, 

 Plymouth, a small form with almost straight ribs. This is a very 

 local, handsome, and uniform shell, which will give no trouble to 

 identify. My finest specimens, from Jersey, are a quarter of an inch in 

 length. Its general aspect resembles O. innovata, but the interstitial 

 striae at the base will always identify it. One of my Jersey specimens 

 has straight ribs and an excavated suture, reminding one of Jeffreys' 

 unique O. formosa. The locality " Aberdeen," recorded for this 

 variety, on my authority, by Mr. James Simpson, 1 is an error. It is 



1 Ann. Scott. Nat. Hist., April, ii 



