Vol. 69. J JURASSIC AMMONITES FROM JE13EL ZAGHUAN. 563 



of the younger shells belonging to this group, and since my cast 

 is septate throughout, it is possible that they never existed on the 

 specimen. The dimensions are: — 



Diameter 80 millimetres. 



Height of the last whorl 57 per cent, of the diameter. 



Thickness of the last whorl 42 per cent, of the diameter. 



Umbilicus 8 per cent, of the diameter. 



These measurements agree closely enough with Waagen's figures, 

 and the flattened sides and gentle slope towards the umbilicus, 

 shown on my ammonite, are also characteristic of the Indian form. 

 On the other hand, the suture-line of the specimen, though worn 

 at the periphery, shows only a subtetraphylloid external saddle, 

 and the first lateral saddle is subdiphylloid ; altogether quite like 

 those of Phylloceras euphyllum Neum. 



No similar intermediate form between the latter, which ranges, 

 according to Neumayr, from the macrocephalvs to the cordatus 

 beds, and the typical Tithonian Phylloceras ptychoieum Quenst. 

 (see especially K. A. von Zittel's ' Stramberger Schichten ' pi. iv for 

 figures) seems to have been described from European deposits. 

 Phylloceras subptychoicum Dacque occurs in India and German 

 East Africa in the ' perarmatum' zone, and differs, as Ave have 

 seen, in its clearly tetraphylloid lateral saddle. According to its 

 author, the Corallian form differs from the younger Ph. ptycho- 

 ieum Quenst. in having on the umbilical side of the external saddle 

 a peculiar leaflet below the summit-branches ; and an identical 

 arrangement is observable on my specimen. 



Phylloceras feddeni Waagen, 1 from the same zone of India and 

 Madagascar, has the external saddle still diphylloid and only 

 the peripheral leaflet shows initial division. The umbilicus in 

 this form is deeper, moreover, and the section wider, coming 

 nearer to the true Ph. ptychoieum (Quenst.). Waagen erroneously 

 gave the thickness as only 22 per cent, of the diameter, but his 

 illustration shows that this figure must at least be doubled. 



Ph. jar aense Waagen 2 has a different section and a rosette of 

 short curved constrictions at the umbilicus. Its suture-line is not 

 unlike that of my specimen ; the external saddle is tetraphylloid, 

 but the siphonal lobe is almost as long as the lateral lobe, and 

 the first lateral saddle is also tetraphylloid. 



Ph. insidare Waagen 3 also has a different section and a very 

 long siphonal lobe. 



With regard to all these forms of Indo-Malagasy affinities, it 

 is interesting to note that Perviuquiere 4 considers the Peri- 

 sphinctes beyrichi, described by Eutterer D from the Jurassic of 

 German East Africa, to be identical with his P. adelus Gemm. 

 found in Tunis and Sicily. 



1 ' Jurassic Fauna of Kutch' 1873, pi. vii, fig. 1 & p. 27. 



2 Ibid. pi. v, fig. 6 & p. 28. 3 Ibid. pi. ix, fig. 3 & p. 29. 



4 ' Etudes de Pal6ontologie Tunisienne : I — Cephalopodes des Terrains 

 Secondaires ' 1907, p. 23. 



5 ' Beitr. z. Kenntn. d. Jura in Ost-Afrika ' Zeitschr. Deutsch. Geol 

 Gesellsch. vol. xlvi (1894) p. 9 & pi. ii, figs. 1-3. 



