858 L. F. Spath — Jurassic Ammonites from East Africa. 



common also in the Batlionien Inferieur of France ". Kilian,^ 

 however, mentions the species from the Bajocian again and states 

 that Lory had found it with A. lunula. It seems possible that P. 

 trijMrtitus or a mutation of that form may go up into the Callovian, 

 but the records of the higher horizons are by older authors, 

 e.g. Quenstedt,^ Pictet,^ and Studer,* and no mention is made of 

 P. tripartitus in the many modern descriptions of Callovian faunae, 

 in which, on the other hand, Lytoceras adeloides is almost universally 

 present. At any rate, Raspail's species is so abundant in the 

 Bathonian of the South of France, that Repelin ^ even speaks of 

 a " zone of Lytoceras tripartitum ". 



Locality. — No. 550, Mwachi River, Pipe-line Crossing, about -^^-. 

 (Together with Phylloceras d. Kunthi Neumayr and Hecticoceras 

 sp. juv.) 



Genus Hecticoceras Bonarelli. 



The specimen described here is an undoubted Oppelid, but its 

 reference to the genus Hecticoceras is somewhat doubtful. Its 

 association with Ammonites that are comparable with Bathonian 

 species suggests affinity with those Bathonian Oppelids that have 

 been put into Hecticoceras by e.g. Hang, Popovici-Hatzeg, and 

 Parona. These forms, on the one hand, seem to be allied to some of 

 the normal evolute " CEcotraustes " of the Parkinsoyii and fusca 

 zones, but not to the early CEcotraustes, such as that figured by 

 Vacek,*^ which has a different suture-line. On the other hand, they 

 probably develop into such more or less involute forms of the 

 niacrocephahis beds as Ojjpelia pleurocyma Parona & Bonarelli,'' 

 or as Oppelia subdisca d'Orbigny sp.® These forms have been con- 

 fused with the earlier and similar Oppelia of i\\it fusca type, and with 

 Oxycerites, groups that are involute and already have a highly 

 specialized suture-line in the Bathonian. To separate, however, 

 the development here indicated from the later and similar 



^ Montague de Lure, Paris (Massou), 1889, p. 79. 



^ A. polystoma Quenstedt is recorded from a " black limestone of macro- 

 cephalus age " from Barreme. 



^ This author {TraitS de Pal., vol. ii, 1854, p. 698) stated that A. tripartitus 

 was characteristic of the Callovian in France, and was found in Germany, 

 together with A. MurcMsonoi. 



* In Geologie d. Schiveiz, 1853, vol ii, p. 45, A. tripartitus is recorded as 

 occurring, with Phylloceras zignodianum a,nd Macrocephalites, in t\ye.CsA\oY\sir\, 

 but on p. 52 it is associated witli S. tortisulcatum. Ph. tatricum, and also 

 A. plicatilis, and put into the Oxfordian. 



•' " Jurass. Chaine Nerthe et I'Etoile " : Bull. Soc. Geol. France, ser. in, 

 vol. xxvi, 1898, p. 520. Ph. niediterraneum and Oppelia here occur with 

 P. trijMrtitus. 



" Loc. cit., 1886, pi. ix, fig. I?,. 8. Buckman (" Certain Jurassic Species of 

 Amm. and Brach." ; Q.J.G.S., vol. ixvi, 1910, p. 96) is inclined to put this 

 as low as the discites zone. 



' Loc. cit., 1897, p. 129, pi. iii, fig. 1. 



^ Loc. cit., Ter. Jurass., p. 421, pi. 146, and Favre, " Contrib. a I'Etude deg 

 Oppelia " : Mem. Soc. Pal. Suisse, vol. xxxviii, 1912, p. 31, 



