RESUME. 123 



Lioceras opalinum. Fig. 11 is that of Lioceras ambiguum variety costatum, and this 

 exhibits differences from the general I/i'oceras-character, in the sutures being 

 farther apart from each other, having a smaller inferior lateral lobe, and partaking 

 more of the Ludwiyia-type, but with apparently more auxiliaries. The superior 

 lateral saddle is also rather deep. How far these characters may be persistent, 

 the cause of them, and what they signify, can only be found out by a study of a 

 more extended series of specimens (see page 80). In fig. 12 is shown a grand 

 suture-line of Lioceras bradfordense variety giganteum, especially noteworthy on 

 account of its large size. The second auxiliary lobe seems to be rather smaller 

 than would be expected, and the third on the edge of the inner margin to be rather 

 larger. Fig. 13 is the suture-line of Lioc. decipiens variety simile; fig. 14 of Lioc. 

 concavum, typical form; fig. 15 of Lioc. concavum variety formosum ; and fig. 16 of 

 Lioc. concavum variety v-scriptum. These are all on the same pattern, but some 

 slight differences in the arrangement of the auxiliary lobes may be seen. Fig. 14 

 shows how the one lobe here penetrates the preceding in the manner characteristic 

 of Lioceras; fig. 15 is chiefly noticeable for the absence of digitations, but I 

 cannot say if this is peculiar to the variety Lioc. formosum or if persistent in that 

 form ; fig. 16 shows that Lioc. v-scriptum is no Ludivigia, 1 but possesses an 

 extremely well-developed Lioceras-\obe-\me ; while fig. 17 shows the small lobe-line 

 of Lioc. ajpertum and indicates that, in spite of a wider umbilicus and consequently 

 narrower whorls, yet all the auxiliary lobes are present. 



The suture-line of the genus Pseudolioceras' 2, is given in fig. 22 from a specimen 

 of Pseudolioc. Beyriclii var. It is noticeable for its large accessory lobe in the 

 siphonal saddle and its array of auxiliary lobes. 



Suture-lines of the genus Hyperlioceras 5 are represented in figs. 23 — 26. They 

 differ from those of Pseudolioceras in having a smaller accessory lobe in the siphonal 

 saddle, a somewhat larger inferior lateral lobe compared with the superior lateral, 

 and a still longer array of auxiliary lobes. Otherwise, fig. 23, taken from a speci- 

 men of Hyperlioc. discites, is very much like the suture-line of Pseudolioceras, and 

 its inner lobes hang down on a slight curve in a similar manner. Fig. 24 repre- 

 sents the lobe-line of Hyperlioc. Wallceri, which is noticeable for the shallowness 

 of its saddles and the shortness of its lobes ; fig. 25 gives the suture of Hyperlioc. 

 discoideum ; and fig. 26 that of Hyperlioc. subdiscoideum. The latter is noticeable 

 for possessing a fewer number of auxiliary lobes, which have also been elevated at 

 the end as if for want of room (I have referred to this at p. 101). The superior 

 lateral lobe is also rather long. 



1 The recurved character of the ribs might suggest Ludivigia; but the absence of the bifurcate 

 ribs, and the inconspicuous character of the ribs on the inner area show a true Lioceras. This deter- 

 mination is fully confirmed by the characteristic suture-line. 



2 Pages 81—88. 3 Pages 88—101. 



