part 1] or the shales-with-' beep.' 75 



occurs in the brooJci bed, and, conversely, no Arietites in the- 

 Black Amioceras Limestone ( = hartmanni bed) ; indeterminable 

 species of Arietites were, however, found 3 feet below and 1 foot 

 above the latter bed. 



From horizon 74r, 9 feet below the birchi-nodul&r, was obtained 

 a new species of Arietites, immature, but with an Asteroceras- 

 periphery, similar to that of Quenstedt's Ammonites brooki /3, 

 just mentioned. 



There is a specimen in the Tomes Collection in the Natural 

 History Museum (C 16501) from Weston Hill (Gloucestershire), 

 marked as occurring ' with Ammonites orookij that probably 

 belongs to the same or an allied, inflated, yet evolute species of 

 Arietites ; it cannot well be compai-ed, however, on account of 

 diffei'ence in size. This example is associated in the same collection 

 with numerous Arietites of the group of A. turneri, A. turgescens, 

 and A. plotti, all from Worcestershire and Gloucestershire ; but 

 there is no true A. brooki. Moreover, those examples that have 

 the inner whorls preserved (C 6154 from Eckington, near Pershore, 

 and C 16506 & C 16884 from Nobb's Farm, Weston) belong to 

 the ' accelerated ' turneri, and not to the early and rather distinct 

 brooTci group. A number of Arietites of the turneri group, kindly 

 sent by Mr. J. W. Tutcher, include examples comparable to the 

 specimen figured by Mr. S. S. Buckman in 'Type-Ammonites' 

 vol. iii (1921) pi. ccxxi. A-B, and A. turgescens, from the neigh- 

 bourhood of Bristol, where the true A. brooki again seems to be 

 missing. A specimen of A. turneri from Ashley Down, and a 

 more distantly costate Arietites from Salford, near Bristol, are 

 associated with Microderoceras. Mr. Tutcher believes that these 

 Arietites come from below the birchi bed, and, according to his 

 statement in 1918 (in S. S. Buckman, Q. J. G. S. vol. lxxiii, 

 p. 280), numerous specimens of Amioceras are associated with 

 Arietites turneri in his district. I am thus not at present in a 

 position to decide whether Mr. Tutcher's turneri zone corresponds, 

 as seems likely, with the birchi zone of this paper (or at least 

 with -post-brook i beds in the Dorset sequence) or whether there is- 

 a condensation of the whole six post-sauzeanupi beds into his one 

 ' turneri zone,' as might also be surmised from Mr. Tomes's- 

 record (in coll.) of Arietites with Agassiceras. 



Two very immature Arietites from the same bed as the new 

 species just mentioned present no indications yet of the keel at 

 diameters of 6 to 7 mm. 



An abundant development of Arietites, notably A. turneri* 

 occurs in the foVc^'-tabular ; and Quenstedt's Ammonites serpen- 

 tinus olifex (pi. xviii, fig. 10), from the Oil-Shale with M. birchi, 

 probably also represents the true Arietites turneri of this 

 horizon. As type of A. turneri, J. de C. Sowerbv's upper figure 

 was selected by Oppel ; the lower figure of pi. cccclii (Min. Conch, 

 vol. v, 1825) is an Amioceras from Watchet, comparable to some 

 of the forms here referred to A. obliquecostatum (Zieten) Fucini. 



