L. F. Spath — Jurassic Ammonites from East Africa. 359 



Lunuloceras ^ would be open to objections from etymological 

 reasons, for A. hecticus itself would then be a Lunuloceras. In any 

 case the definite relations of the many forms referred to the genus 

 Hecficoceras remain yet to be worked out, also the connexion with 

 Op2')eUncB helow and the Ochetoceras-Trimarginites fauna above. 



Hecficoceras sp. juv. (PI. I, Fig. la-c.) ■■ 

 Compare : — 

 1905. Hecticoceras Haugi, Popovici-Hatzeg, " Les Cepli. Jurass. M. 

 Strunga " : Mem.,Soc. Geol. France, Pal., No. 35, p. 18, pi. iv, 

 fig. 3, pi. V, figs. 2- 10. 



Dimensions. — Diameter . . 8" 3 mm. 



Height of the last 



whorl . . 40 per cent of the diameter. 



Thickness . . 32 



Umbilicus . .30 ,, ,, ,, 



Description. — This sjDecimen represents only the inner whorls of 

 a larger ammonite since it is septate throughout. The periphery 

 shows a keel only on the last two-thirds of the outer whorl, and the 

 earlier portion of the shell is perfectly smooth, with flat sides and a 

 rounded venter. The open umbilicus has steep but rounded walls. 

 The ornament which is shown near the end of the shell (in the form 

 of about six costas) is distinct near the periphery only ; and only 

 one or two of these obscure folds seem to be very indistinctly 

 continued, with a lateral forward bend, on the sides, though they do 

 not reach the umbilical border. There is an indication near the end 

 of the specimen of a differentiation of the periphery into lateral 

 zones (on each side of the keel) marked off from the sides by an edge, 

 whereas on the previous portion of the last whorl the ventral area 

 is rounded and gradually passes into the sides. 



The suture-line consists of a deeply forked, trifid principal lobe, 

 much deeper than the external and second lateral lobes, of irregularly 

 bifid external first and second lateral saddles, and of three auxiliary 

 lobes, slightly raised towards the umbilicus. 



Observations. — The suture-line of this specimen is very similar 

 to that of a young Lunuloceras, and agrees in all essentials with that 

 of " Harjyoceras " lunula (Zieten) given by Noetling,^ or with the 

 suture-lines of a number of specimens of this almost universal 

 species-group from many different localities. On the other hand, 

 the suture-line of young Oppelids from the zigzag hemera of Power- 

 stock Station, Dorset, is also very similar to that of the specimen 

 here described, as is that given for Oppelia suhradiata (Sowerby) 

 var A. by Favre.^ With a very immature specimen it is a matter 

 of opinion whether it should be considered as allied to the Bathonian 



1 Tsytovitch (" Le genre Hecticoceras " : Mem. Soc. Pal. Suisse, vol. xxxrii, 

 1911) has again drawn attention to the difficulty of separating Hecticoceraf 

 and Lunuloceras on purely morphological grounds. 



^ Der Jura am Hermon, 1887, p. 18, text-fifj. 3, 



3 Loc. cit., 1912, fig. 1 on p. 13. 



