TEMNOCHEILUS. 81 



depressed by tlie next whorl ; the ratio of the diameters being as 3 : 5. Whorls 

 increasing rapidly. Sutural line slightly concave laterally, roundly convex as it 

 turns the angle of the sides, and again slightly concave on the back. Chambers 

 fourteen in a whorl, very slightly convex at the highest lateral point. Body- 

 chamber one half the whorl. Shell very thin, apparently of two layers, marked 

 (near the mouth) with very fine and crowded concentric striae, a few of which are 

 more prominent than the rest. Mouth apparently bilobed, being somewhat 

 excavate at the centre of the back. 



Size. — 100 mm. high, 80 mm. wide, 68 mm. deep. 



Locality. — Wolborough. A single but very fine specimen in the Museum of 

 Practical Geology in Jermyn Street. 



Remarks. — This remarkable fossil is labelled Newton Bushel in the Jermyn- 

 Street Collection, biit it is not weathered in the peculiar manner of many of the 

 other fossils from that locality, and therefore, whether it actually came from 

 Wolborough Quarry or from some other locality in the neighbourhood is a matter 

 of some uncertainty. The matrix is hard, shelly limestone, and the fossil is 

 almost entirely decorticated, and is covered in places with patches of yellow ferru- 

 ginous sand, thus differing considerably from the usual character of Wolborough 

 deposits. As, however, the name Newton Bushel was formerly applied to all 

 Wolborough fossils, the presumption is that it came from there. It is to be noted, 

 however, that the name of the locality given by the label and the museum books 

 is the sole evidence that it came from Newton. 



Affinities. — The species appears to be very closely allied to Nautilus suhtuher- 

 eulatus, Sandberger,^ agreeing with it in general shape and in the curvature of its 

 chambers, but clearly distinguishable by the absence of tubercles, and by being 

 comparatively deeper, with a less rapidly increasing spire, and without the slight 

 ridge in the centre of the back seen in the German shell. That species has a 

 small rounded tubercle on the lateral edge of every fourth chamber, and the ratio 

 of the section of the whorls is 3 : 4, instead of, as in ours, 3:5. A fragment 

 described by F. A. Romer^ under this name differs from Sandberger's type in 

 having no syphonal ridge on the back, and only a single tubercle, though it 

 consists of nearly half a whorl. In its other features, however, it agrees with its 

 type, and not with our shell. 



Hercoceras mirum, Barr.,^ is distinguishable by the presence of numerous horn- 

 like lateral tubercles or spines, by the siphuncle being large and visible on the 

 back of the cast, and by the greater width of the section of the whorls. On his 



1 1851, Sandberger, ' Verst. Rhein. Nassau,' p. 133, pi. xii, fig. 3. 



2 1860, F. A. Eomer, 'Beitr.,' pt. 4, p. 158, pi. xxiv, figs. 5 a, b. 



^ 1865, Barrande, ' Syst. Sil. de Bohorne,' vol. ii, p. 153, pi. xlii, tigs. 1 — 8, and pi. cii, figs. I — 9, 

 Et. Gl. 



