MARSHALL: ADDITIONS TO 'BRITISH CONCHOLOGY.' 253 



variety. It has the dimensions and general appearance of 

 O. pHcata^ but the latter has a stronger tooth which is 

 always visible, and the suture is shallower. 



O. acuta var. gracilis Marsh. Shell more slender through- 

 out. From Torbay and the Channel Islands. 



O. acuta var. attenuata. Spire much longer and attenuated, 

 suture slighter, whorls more flattened, mouth longer and 

 narrower, and umbilicus smaller. Guernsey, 20 fathoms, 

 rare. Resembles in shape EuH?iia distorta var. gracilis. 



O. turrita var. nana Jeff. A mvcivXt fac-simile oi the type. 

 This occurred to me many years ago (1872) from Skye, 

 and was shown to Dr. Jeffreys, who adopted and published 

 the name. I have it also from Millport in Cumbrae, and 

 from Torbay ; in all cases living in sea-weeds at low-water. 

 It has also been recorded from the Mediterranean and 

 Teneriffe. There is a dwarf form of O. turrita not un- 

 common which is less than a line in length ; but the var. 

 nana does not exceed half-a-line. 



O. pllcata var. carinata Marsh. Having a keeled periphery. 

 Habitat : St. Aubin's Bay, Jersey, with the type. About 

 twenty per cent, are so keeled, some of them more strongly 

 than 0. condidea. 



O. insculpta var. laevissima Sars. Shell quite smooth. 

 Habitat : Norway, in deep water (Sars). In this country 

 it occurs at Gairloch in 30 fathoms, and in the Minch 

 50 — 70 fathoms. 



O. diaphana var. inflata Marsh. Shell broader throughout ; 

 whorls more convex, the last one particularly so. Re- 

 sembles O. insculpta var. Icevissi/na, with which it lives in 

 the Minch, in 50 — 70 fathoms; but the tooth and umbilicus 

 of the former enable the two forms to be separated without 

 difficulty. 



O. warren i var. intermedia Marsh. Having the oval body- 

 whorl and short spire of O. obliqua, but retaining the basal 

 striae, the umbilicus, and the truncated apex of 0- tvarreni. 



