L. F. Spath — Jurassic Ammonites from East Africa. 357 



of France ^ at a whorl height of 3'75 mm. the thickness amounts to 

 3'25 mm. and the ratio increases to 8"75 : 6'25 mm. Further, 

 in the typical specimens the constrictions begin with a more decided 

 forward bend from the umbilicus. On the other hand, there is 

 almost i^erfect agreement in the suture-line, both external and 

 internal ; so that even if the East African specimen cannot be 

 identified with P. fripartitus, it, at any rate, must belong to a closely 

 related form. 



Lytoceras tripartitiforme Gemmellaro,^ which also occurs associated 

 with Phylloceras Kudernatschi Hauer sp., Ph. rlisputahile Zittel, 

 and other forms of the Klaus Beds, is distinguished from the specimen 

 here considered by the different course of the constrictions. This 

 difference also separates the East African example from L. 

 polyhelictwm ( Boeckh), a form of the Parkinsoni zone of Hungary and 

 Daghestan, and considered to be near to P. tripartitus by Neumayr et 

 Uhlig.^ The whorl-section of L. jjolyhdictum is more like that of the 

 present specimen than is the compressed shape of P. tripartitus ; 

 on the other hand, the three saddles shown in the suture-line of the 

 Daghestan form, given by the latter authors, are different from those 

 shown in Fig. 6c. 



Lytoceras 'polyanchomenimi Gemmellaro,^ from the macroceplialus 

 beds of Sicily but recorded also from the Swiss Oxfordian,*^ may 

 agree with the specimen here examined in whorl-section and 

 possibly in the constrictions,® but the suture-line of the East African 

 specimen certainly does not show the lateral branch of the dorsal 

 lobe continued on to the lateral area. 



Horizon and Distribution. — P. tripiariitus is a very common 

 ammonite in the zones of Oppelia fusca and Zigzagiceras zigzag 

 (Bathonian) in the South of France,'' and also occurs in the Bathonian 

 of Italy, Switzerland, Austria, and the Carpathians. Hochstetter ^ 

 records the species even from the Lower Bajocian, but his specimens 

 were badly preserved, and on the following page of the work quoted 

 he calls P. tripartitus, " of the Bathonian, a younger form of the 

 group of Lytoceras quadrisulcatum.'' He recorded® sixty-five 

 specimens from the Bathonian of St. Veit, and added that Griesbach 

 already had called this species " abundant and easily identifiable, 



^ There were no specimens available for comparison, but the writer was 

 immediately supplied (through the kindness of M. Stuer, of Paris) with three 

 prototj^pes of Raspail's from Aix (see Hang, loc. cit., 1908, p. 1022) and four 

 specimens from Chaudon, Basses-Alpes (ibid., p. 1023). 



2 Loc. cit., 1877, p. 135, pi. xix, fig. 9. 



3 Loc. cit., 1892, p. 39, pi. iii, fig. 2a-d. 

 * Loc. cit., 1872, p. 14, pi. iv, figs. 2, 3. 



^ Favre, " Descr. Foss. Terr. Oxf. Alp. Frib." : Mem. Soc. Pal. Suisse, vol. iii, 

 1876, p. 35. 



® According to Gemmellaro's description, not the figures cited. PL iii, fig 3, 

 in Favre (loc. cit.) is very near, being the j'oung. 



' Haug, loc. cit., 1908, pp. 1019-53. 



« Loc. cit., 1897, p. 109, 



=* Ibid., p. 143. 



