Sept. SAGITTICERAS 19 



1920 



with P. bathyomphalum. St. Ives, Hunts ; Mr. Tutcher's Coll., Holotype, 

 S. 34, 48, 70, 23.5 ; 59, 43, 75, 25 ; size 63 mm. ; max. c. 90 mm. 



P. pavlowi, R. Douville sp. Quenstedticeras pavlowi, R. Douv., 

 op. cit. 1912, xi, 13, Holotype, F. 57, 39, 81, 26 ; 70, 44, 81, 26, not taken 

 at end, as this seems damaged. Paratype, Russian example, R. Douv., 

 Id. p. 74, figs. 80-82, F. 53, 38, 79, 27 ; 98, 45, 90, 25.5. Mr. Tutcher's 

 specimen, Genoholotype, from St. Ives, Hunts, Oxford Clay, S. 35, 40 ? 

 74. 23 ? ; 55. 43, 82, 25 ; PI. CLXX. 



P. roberti nom. nov. Holotype, Quenstedticeras sutherlandice ; 

 Robert Douville, 1912 (non Murchison sp.), op. cit. XI (v), 8 only. 

 An involute development of P. pavlowi with the thickness beginning to 

 decrease from that of the Russian example of that species, and the 

 periphery becoming rounder, foreshadowed in the same form. F. 54, 

 41, 82, 16.5 ; 104, 46, 82, 21.5, Normandy. 



The proportions of the last two species, especially the agreement 

 in thickness, are fair evidence for their relationship. The next species 

 after P. roberti might be more involute in youth, would be excentrum- 

 bilicate in adult — the starting indicated in the proportions of P. roberti 

 given above — thinner, and perhaps attaining smoothness. It may have 

 been confused with Am. goliathus or Am. sutherlandice in collections. 



Sagitticeras g. n. Genoholotype, S. sagitta nov. Serpenticonic 

 becoming tumid ; periphery 2 to 1 c ; ornament 4, coarse, ribs laminar ; 

 crest-like bullae, OVL 2 ; similar bullae less strong, EL. Like Verte- 

 briceras — the genotype especially has resemblance to V. rliachis (III, 

 p. 16) ; but a keel is not developed — instead strong ribs of V ertebriceras 

 pattern cross the periphery with V curves or arrow-like, the apices 

 rising to little transverse crests ; and against these apices, leaning back- 

 wards, are little buttresses, whose bases point forwards, but die away 

 before touching next V. The presence of these buttresses, with their 

 consequent slight raising of the median line of periphery, gives a suggestion 

 of keel bordered by feeble depressions of the V ertebriceras pattern, but 

 only when the specimen is held at certain angles to the light. Ribbing 

 strong, of V ertebriceras pattern, the ribs run sufficiently forward on 

 periphery to throw radial line all behind guide line. Ribs rise nearly 

 radial from contact-line, not with the strong backward sweep of V erte- 

 briceras. In general characters of development the genus is between 

 Vertumniceras and V ertebriceras. England (Dorset, Huntingdonshire) 

 Argovian, pve-Goliathiceras, perhaps intermediate 4 and 5. 



S. fastigatum, nov. Whorls somewhat flat-sided, with distinct 

 inner margin and a fastigate periphery. The periphery is like that of 

 Vertumniceras damoni (Y.T.A. CXVIb), but ribs do not make so sharp 

 a V. Ribs are less projected forwards than in S. sagitta — otherwise 

 ornament is similar, but not so developed. Umbilicus is gradate. 

 St. Ives, Huntingdonshire [Oxford Clay, grey argillaceous matrix] ; 

 Mr. Tutcher's Coll. ; S. 51, 44, 49 (43), 33. 



The question now arises whether Am. vertumnus, Damon, 1880, 

 I, 3 = Querist, damoni, Nikitin, (see Y.T.A. 116 c), is the same species 

 as the Yorkshire example (Y.T.A. CXVIb). It looks as if the Dorset 

 species had the laminar ribs with slight forward projection of this genus : 

 if so, it would be the species before S . fastigatum. The Yorkshire species 

 is rightly a Vertumniceras, but would then have to take another trivial 

 oame. 



2. S. sagitta, nov. Whorls tumid, rising with a somewhat 

 gibbous curve from inner edge till they meet a flatly-arched broad 

 periphery — at the meeting place are strong somewhat crest-like bullae, 



