part 4] JURASSIC CHROXOLO(tY : LIAS. 325 



Fig-s. 3 a-3 d. Gleviceras mPARivM (Oppel), p. 292. 



Fig-. 3 a. Side view, last half of wliorl somewhat crushed ; fig. 3 h, peripheral 

 view of first half of whorl ; fig. 3 c, peripheral view with ribs, 

 auriculoids, and their connecting pseudo-carina marked diagram- 

 matically : fig. 3 d, part of side view with auriculoid marked dia- 

 grammatically, also sutiu-e-line (approximate) : the incipiently- 

 trilobulate superior lateral lobe is on the edge of the periphery in 

 line with auriculoids. All figures X 2. Lower Lias 'oxynotum,' 

 Aston Cross, Tewkesbury (Gloucestershire) [Deiran, hifenini ?;]. 



Fig. 4. Gleviceuas glevexse, nom. nov., p. 289. 



Fig. 4. Radial line and rib-scheme of example figured in PI. XXYII. fig. 3, and 

 PL XXIX. figs. 3 a-3 c. marked diagrammaticallv in photograph, 

 X 2. See also PI. XXVII. fig. 2 & PL XXVIII. figs. 1-2, for 

 illustrations of other examples. 



Figs. 5 a & 5 &. Gleviceras avritulvmI glevexse, p. 291. 



Fig. 5 a. Suture-line of specimen figured in PL XXXI, figs. 1 a & 1 6, marked 

 in diagrammatically on the photograph ; fig. 5 h. rib-scheme with 

 auriculoids similarly marked in : both figures X 2. 



Plate XXXI. 

 [A white X marks the beginning of the body-chamber.] 

 Figs. 1 a & 1 b. Gleviceras avmitvlvmI glevexse, p. 291. 



iFig. 1 o. Side view ; fig. 1 6, peripheral view ; both figures X 2. From Lias, 

 Charmouth (Dorset) [Bed 92] ; Coll. James Francis. [Deiran, 

 Gleviceras ?/.] See PL XXX, figs. 5 a & 5 b. 



Figs. 2a & 2 6. Arxioceras flavum, nom. nov., p. 298. 



Fig. 2 a. Side view; fig. 2 &, peripheral view; holotype ; Lias Limestones, 

 Lyme E-egis (Dorset) [Lymian, Arnioceras ?/]. 



Figs. 3a-3cZ. Aexioceras axagexeticviii, sp. nov., p. 300. 



Fig. 3 a. Side view ; fig. 3 b, apertural view ; fig. 3 c, peripheral view, taken 

 at the end of the whorl, showing ribs, nodes, keel, and incipient 

 sulci — all these figures are of the natural size ; fig. 3 d, part of 

 whorl, showing suture-lines, X 2. Lias Limestones. Lyme Regis 

 (Dorset) [Lymian, Arnioceras ?/]. 



Figs. 4a & 4 6. Arxioceras eortvxatvm, sp. nov., p. 301. 



Fig. 4a. Side view, naturaLsize; fig. 4b. suture-lines, approximate delineation 

 of last one, not clearly shown, taken at X . Lias, Paulton, near 

 Radstock (Somerset) [Lymian, Arnioceras t;]. See PL XXVIII, 

 fig. 4. 



Fig. 5. Arietites tvrgescexs, sp. nov., p. 296. 



Fig. 5. Part of periphery, with rib-curves marked diagrammatically, showing 

 change after loss of keel. See PL XXIX, figs. 2 a & 2 b. 



Discussion. 



Mr. W. D. LA>^a said that, wliile heartily welcoming the paper, 

 he would wish to criticize it from two points of view. 



(1) In applying the principle of famial dissimilarity, the 



