L. F. Spath — Jurassic Ain')nonites from East Africa. 313 



spiral lines along the periphery, forming a peculiar feature of the 

 test in this specimen, still persist. The extremely fine radial lines 

 describe a strong forward curve on the inner third of the lateral area, 

 bend back again towards the outer third, and near the periphery 

 once more swing gently forward, aftex the style of the ornament in 

 Popovici-Hatzeg's good photographs. Though the ornament is worn, 

 some of the costae are more prominent than others, and it seems 

 probable that the ornament was that typical of Phylloceras 

 Kudernatschi. It also appears that the test consisted of four layers, as 

 in Phylloceras. Malayanum G. Bohm, described by both the author of 

 that species^ and byDacque,^ namely a smooth inner layer, a weakly 

 costate second layer, followed by the lineate third layer with its 

 peculiar string- or tube-like costse, easily detached and preserved (in 

 the specimen under examination) only in one or two places. The 

 fourth (smooth) outer layer of the test is absent. The ventral area is 

 slightly compressed as in the section given by Jussen,^ yet 

 regularly rounded ; and the greatest thickness of the whorl is about 

 midway between the periphery and the umbilicus. The latter is very 

 narrow, funnel-like, and very deep, with the sides regularly rounding 

 into it. 



The suture-line could not be exposed plainly enough for complete 

 delineation, but apart from the six saddles shown in Fig. \c (drawn at 

 a diameter of about 30 mm.) there are probably two or three more 

 monophyllic saddles on the umbilical slope. The external saddle is 

 very distinctly diphyllic, the first lateral saddle tetraphyllic, and the 

 following three saddles diphyllic again. 



Observations. — The small umbilicus and linear ornament of this 

 specimen, together with the absence of constrictions, characterize 

 it as a member of the heterophyllum group of the genus Phylloceras, 

 which group ranges from the Lower Lias up into the Cretaceous. 

 Its general shape and suture-line seem to agree very well 

 with Phylloceras Kudernatschi (Hauer). According to Neumayr, 

 Gemmellaro, and Jlissen, the umbilicus of that species amounts to 

 7 per cent of the diameter, whereas the figures given by Popovici- 

 Hatzeg show a smaller umbilicus, comparable with that of the 

 present specimen. There also is some variation in the whorl-shape. 

 Kudernatsch's type (pi. i, figs. 5 and 6) shows the greatest thickness 

 near the middle of the whorl, whereas his smaller specimen (figs. 8 

 and 9) and the ammonite figured by Neumayr have the region of 

 greatest thickness nearer the umbilicus. On the other hand, the 

 excellent photographs given by Popovici-Hatzeg show a laterally 

 flattened whorl. Apart from the slightly larger umbilicus of 

 Jiissen's figure (not in agreement with that of Fig. la, and therefore 

 probably drawn too open) the section given by that author best 



1 " Beitr. Geol. Nied. Ind." : Palmontogra phka , Siipp., vol. iv, pt. i, 3. 

 " Oxford V. Wai Galo," 1907, pi. xiv, figs. 46, 5. 



2 Op. cit., 1910, pp. G, 7, pi. i, figs. 1-3. 

 - Op. cit., 1890, pi. ii, fig. 16. 



