316 L. F. Spath — Jurassic Aintnonites from East Africa, 



characterize the specimen as a member of the group of Ph. ketero- 

 phyllum, and it is probable that it belongs to the same lineage as, 

 and is a near relative of, Phylloceras Kmlernatschi Hauer. 



Locality.— This specimen (No. 551) was found (isolated) to the west 

 of the Mwachi River, about V- 



Phylloceras cf. Kunthi Neumayr. (PI. V, Fig. 3a-c.) 



1871. PIi!,'llocera< Kunthi Nenmayr, " Jurastudien," ii: Joe. cit., p. 312. 



pi. xii, fig. 6 ; pi. xiii, fig. 1. 

 1905. Ph. n.sp. ind., Popovici-Hatzeg, " Les Cej^h. Jurass. Moy. Mt. 



Strunga " : loc. cit., p. 11, pi. iv, fig. 8. 

 1910. Ph. cf. kunthi (Neumayr), Till, "Amm. Faunad. Kelloway v.Villany " : 



loc. cit., p. 253. 



Dimensions. — Diameter . . 19 mm. 



Height of the last 



whorl . . 59 per cent of the diameter. 



Thickness . . 36 ,, „ ,, 



Umbilicus . .5 ,, ,, ,, 



Description. — This specimen is a wholly septate cast and has only 

 a small portion of the test preserved, namely, on the periphery, 

 near the beginning of the outer whorl. Here the ornament consists 

 of distinct radial striae (about eleven to the 2 mm. of test shown) 

 after the manner of Phylloceras Velledce Michelin sp. It is a little 

 thinner than the two forms j)reviously described ; in its elongate 

 elliptical section it more resembles that referred to Ph. Kudernatschi, 

 The whorls show their greatest thickness about midway between 

 the periphery and the umbilicus ; the latter is narrow and deep. 



The suture-lines are well exposed throughout the last whorl. 

 Apart from the eight saddles shown in Fig. 3c there are three more 

 saddles externally, and about seven saddles internally, making 

 altogether about seventy elem.ents. The external saddle shows 

 branching of its terminal leaflets (after the manner of Ph. serum 

 Oppel sp. and Ph. semisulcatum d'Orbigny sp.), and the first lateral 

 saddle becomes triphyllic owing to the leaning over of its originally 

 tetraphyllic summit to the ventral side. The three saddles following 

 this are diphyllic, the next six monophyllic. 



Observations.- — The absence of constrictions and other points 

 characterize this specimen as a form of the group of Ph. hetero- 

 fhyllum. Though in dimensions and whorl-shape it resembles the 

 ammonite above referred to Ph. Kmlernatschi, its complex suture- 

 line distinguishes it at once from that species. The subdivision 

 of the terminal leaflets of the external saddle, however, is indicated 

 in Neumayr's figure of the suture-line of Ph. Kudernatschi,^ though 

 this subdivision is more reminiscent of Ph. subohtusum Kudernatsch 

 and many forms of the group of Ph. tatricwn Pusch. 



The slender whorl-section of this specimen is not unlike that of 



' Loc. cit., pi. xii, fig. 4c. 



