SIPHO OURTUS. 179 



Remarlcs. — It is clear that Jeffreys was familiar with the specimens figured by 

 Wood in 1848 as 8. gracilis} At the same time he seems to have had in mind some 

 of the smaller Crag fossils, as his remark that those he called Fnsus curtiis were 

 smaller than 8. gracilis, having a short spire, does not seem descriptive of all those 

 which I consider to be varieties of the former. 



Mr. Friele has identified with 8. curtiis some shells more or less nearly allied to 

 8. togatus (grouping the latter and several other species under the former name) 

 which were dredged by the Norwegian North Atlantic Expedition at a number of 

 places off the coasts of Norway, Finland and Spitzbergen, at depths of from 60 to 

 658 fathoms. Of these he figures six, varying considerably inter se, but only 

 within certain limits ; some of them occur in the Crag, but very rarely. As a 

 rule, the shells to which I propose to confine the term S. curtus are, on the 

 contrary, common in our East Anglian deposits and differ widely from them. Of 

 these I may mention the variety incurvata (PI. XXI, fig. 6), a strong shell with a 

 rather long canal, turning abruptly and decidedly to the left ; it corresponds more 

 or less nearly with Wood's Troplion gracAle (tab. vi, fig. 10a, 1848), and is fairly 

 common at Oakley and at other horizons of the Red Crag ; this, with PI. XXI, 

 fig. 1 of the present memoir, which may perhaps be regarded as the type, and a 

 third, var. sollda (fig. 3), are thick and coarse-looking; the latter approaches some 

 Recent specimens of 8. gracilis var. convoluta in my collection, but may be referred 

 more appropriately, I think, to the present species. A second group of a somewhat 

 similar character, on the contrary, have a smooth and polished appearance, 

 including var. lata (fig. 7), var. brevicaiidata (fig. 4), var. exilis (fig. 8), and one, var. 

 longicaudata (fig. 5), with a shorter spire and an exceptionally long canal which I 

 have been tempted to regard as specifically distinct. 



All these shells are more or less allied, having certain features in common ; 

 they are strong and solid, sometimes very much so, their sculpture is generally 

 inconspicuous, the whorls are convex, and the canal turns decidedly to the left. 



In the specimens figured by Mr. Friele under the present name the canal is 

 nearly straight, the sculpture is stronger, and the texture of the shell thin and 

 fragile. The latter feature may possibly be due to the different conditions under 

 which they lived. It should be noted, however, that we find other species of Sijjho 

 at Oakley and elsewhere in the Red Crag of a thin and fragile character. 



Among the species grouped by Mr. Friele as 8. curtiis he includes, as just 

 stated, some having strong spiral sculpture, as, e.g., Fusus togatus, Morch, and 

 Buccinum 8abinii, Oray, which have been considered by other conchologists as 

 distinct. Such shells, however, together with 8. cordatns, A. Bell, when occurring 

 in the Crag, are easily separated from the various varieties of 8. curtus just described. 

 The latter form by themselves rather an unwieldy group ; it seems to me desirable, 



1 See Brit. Conch., vol. i, Introduction, p. xc, 1862. 



