L. F. Spath — Jurassic Ainmonites from East Africa. 355 



according to Kilian ^ does not persist into the Boissieri beds of tlie 

 lowest Neocomian. The type itself is Callovian and of wide 

 distribution, both in the Alj)ine-Mediterranean region, as far as the 

 Caucasus, but (with related forms) also in Wurtemberg. 



Locality. — No. 10, from the grey, otherwise unfossiliferous 

 limestone, beside the break-pressure tank, mile ^^ on the Mombasa 

 Pipe-line (together with Phylloceras of. disputabile Zittel). 



Genus Protetragonites Hyatt. 



Hyatt 2 created this genus for Lytoceras quadrisulcatum d'Orbigny 

 sp., a form that is very abundant in the Lower Valanginian,^ though 

 similar ammonites occur in the Tithonian.^ Vacek ^ traced the 

 group of L. quadrisulcatum back to his Bajocian L. rasile, and 

 included ^ in the same group L. rubescens Dumortier sp. and 

 L. n.sp. ind.,'' which forms are assigned to the genus Megalytoceras 

 S. Buckman by its author.® Vacek remarked that the Tithonian 

 Lytoceras municipale Oppel sp. was so near to L. rasile that in spite 

 of the enormous chronological separation one might almost be 

 inclined to consider them specifically identical. The writer is not 

 convinced that the Tithonian-Neocomian quadrisulcatus groap 

 {=^ Protetragonites s.str.) can be traced back even to the Bathonian 

 Lj. tri-partitum Raspail sp., and, in fact, considers the latter to rec^uire 

 a new generic name since its suture-line alone clearly distinguishes 

 it from the other Lytocerata. Owing, however, to lack of material 

 and consequent inability either to prove the independence of this 

 group with the necessary precision, or to trace its relations to 

 such forms as L. rasile Tornquist -non Vacek," L. trij)artitiJorme 

 Gemmellaro, etc., the specimen to be described here is provisionally 

 referred to the genns Protetragoniies. 



Protetragonites cf. tripartitus Raspail sp. (PL I, Figs. 6a-c.) 



1829. Amm. tripartitus Raspail, Ann. Sci. Obs. (Lyce, 1831), pi. xi, fig. 5, 

 pi. xii, fig. 7. 



1841. A. quadrisulcatus d'Orbigny, Ter. Cret., p. 151, pi, xlix, fig. 3. 



1842. A. tripartitus (Raspail), d'Orbigny, Ter. .Jurass, p. 496, pi. 197, figs. 1-4. 

 1846. A. poly stoma Quenstedt, Cephalopoden, pi. xx, fig. 8. 



1860. A. tripartitus (Raspail), Ooster, Cat. Ceph. foss., p. 66, pi. xvii, figs. 1-3. 



^ Lethcea geognostica, ii, Mesozoicum, vol. iii, Kreide, pt. i. Unterkreide, 

 fasc. 2, 1910, p. 171. 



2 In Zittel's Text-book of Palteontology, edited by C. R. Eastman, vol. i, pt. ii. 

 1900, p. 569. 



* See e.g. Kilian, Lethcea geognostica, ii, Mesozoicum, vol. iii, Kreide, pt. i, 

 fasc. 2, 1910, p. 174. 



* Ibid., p. 171, and Sayn ("Amm. Pyrit. Marnes Valang, S.E. France" : 

 Mem. Soc. Geol. France, Pal., No. 23, 1901, p. 2) identifies his Valanginian 

 specimens with Zittel's Tithonian ammonites. 



5 Loc. cit., 1886, p. 64. 

 « Ibid., p. 60. 



■^ Ibid., p. 64, pi. i, figs. 6, 7. 



** " On certain Genera and Species of Lytoceratida3 " : Q.J.G.S., vol. Ixi, 

 1905 I). 151. 

 « Loc. cit., 1898, p. 28 (160), pi. v, fig. 8. 



