imperfectly-defined SjJecies of Jurassic Nautili. 277 



numerous septa, and in the siphuncle, which, instead of being 

 near the centre, as in the type (lower figure of Sowerby's 

 plate), is above. To this form we have therefore given a new 

 nam e — Na u tilus pseudo lin ea t us. 



Nautilus lineatus must now be restricted to shells of a 

 somewhat robust habit of growth, with flattened sides and 

 broad flattened periphery, closed umbilicus, numerous, very 

 slightly flexuous septa, and a nearly central siphuncle. It 

 may be added that the shell had a perfectly smooth surface. 



The name lineatus, which was clearly intended by its 

 author to have reference to the faint ridge seen upon casts 

 along the median line of the periphery, has apparently misled 

 many palaeontologists, for we have seen in collections various 

 Jurassic Nautili labelled " lineatus " which certainly belonged 

 to more than one species. In point of fact this median line 

 or ridge is the " Normallinie " of the Brothers Sandberger *, 

 and cannot be used as a specific character, since it is found 

 not only in numerous species of the Nautilidae, but also in 

 some species of the Orthoceratidse. 



The following species are evidently closely related, viz. : — 

 Nautilus lineatus, N. pseudolineatus, sp. nov., N.polygonalis\, 

 and N. glaber, sp. nov. 



Horizon. Inferior Oolite. 



Locality. Yeovil, Somersetshire. The specimen already 

 referred to as bearing one of Sowerby's labels (" Nautilus 

 lineatus, M. C. 41 ") is not localized. 



8. Nautilus pseudolineatus, sp. nov. 



Sj>. char. Shell subcompressed, flattened upon the sides 

 and periphery, the latter being moderately broad and having 

 a subangular border. Umbilicus closed. Whorls about 

 three, increasing rather slowly in diameter. Body-chamber 

 occupying about half a volution ; aperture wider than high. 

 Septa rather deeply concave, nineteen or twenty in the last 

 whorl, the last two very approximate. Sutures forming a 

 sigmoid curve on the sides of the shell and a slight sinus on 

 the periphery. Siphuncle rather large, subcentral. Test 

 thick, smooth. Anterior border of muscular impression well 

 defined, broadly arched (see fig. 9). 



Bemarks. The greatest diameter of the largest specimen in 

 the Collection (no. C. 324) is 6^ inches. 



The slow rate of increase of the whorls in this species is 



* ' Die Versteinerungen des rkeinisclien Scliichtensystems in Nassau,' 

 (}. and F. Sandberger, 1850-56, p. 41. 



t J. de 0. Sowerby, Min. Conch, vol. \i. p. 56, pi. dxxx. 



