﻿BRITISH FOSSIL CEPHALOPODA, 191 



expansion takes place, which is the commencement of the elliptic curve, which has 

 a long axis of 3| inches. The body-chamber continues the curve of the septal part 

 without discontinuity, thus contracting to the aperture ; round this there is a broad 

 depression parallel to the ornaments, which gives a produced appearance to the 

 margins of the aperture. The shape of this is not properly seen : what is really 

 the smaller opening is on the slanting surface. It is elliptic, with long axis in 

 the antero-posterior direction, and the passage of junction is short and moderately 

 narrow, but the apex which should show the larger aperture is broken away. On 

 the side of the small aperture are seen, most marked near the middle line, a series 

 of fine strige, 4 per line, bending away from the aperture on both sides, and coming 

 to a rounded angle on the middle line. These are grouped by the occurrence of 

 stronger ones at about the interval of a chamber. They are feebler and direct on 

 the opposite side, but are continued on the first side over the earlier cylindrical 

 portion. The septa have, as usual, very little convexity, and are distant about -jlj-the 

 largest diameter apart. The sutures are nearly direct, but make a very feeble sinus 

 backwards on the side of the small aperture. The siphuncle is not seen in this 

 example, but in another figured by Sowerby, and as stated by him it is situated half- 

 way between the centre and the outside ; it is bulbous, the bulbs having a diameter 

 -§ that of the chamber. In the Lower Ludlow rock, Leintwardine Hill. In the 

 Museum of the Geological Society. 



General Description. — This species cannot be made to include all the elliptic- 

 shaped Gomphocerata without ignoring differences on points of as great importance 

 as the shape. The true form has a transverse elliptical section, with the shorter axis 

 in the plane of symmetry, the two axes being in the ratio of about 5 to 6. The 

 longitudinal section is also uniformly elliptical, the earlier end being truncated ; 

 the diameters of this ellipse being in the ratio of 2 : 3. The greatest transverse 

 diameters are opposite the space included between the last septum and the last but 

 two. There is a little tendency to inflation of the body-chamber on the ventral 

 side, and the aperture is bounded by a broad depression. It consists of a small 

 opening on the ventral slope, a slightly contracted passage, and a large aperture, 

 having its longer axis transverse and twice the length of the shorter ; the apex of 

 the shell lies between the centre of the large aperture and the middle of the passage. 

 The surface is usually lost, but one other example than the type shows well-marked 

 lines of growth — curving backwards on the ventral side — and most marked beneath 

 the smaller aperture. The sutures are very slightly oblique on the side, going 

 back towards the ventral line. The septa are distant from y 1 -^ to T 2 ^ the greatest 

 transverse diameter apart. The last chamber is generally of half-size. The con- 

 vexity of the septal surface seems to vary from \ the diameter downwards. The 

 siphuncle is situated on the short diameter nearer the ventral side, from -g- to ^ the 

 diameter from it. Its elements are bulbous, with a transverse diameter in the ratio 



