L. F. SpatJi — Jurassic Avimonites fro'^n East Africa. 315 



and the periphery thus appears more rounded. The umbilicus is 

 very small and deep, and the sides are regularly rounded into it. 



The suture-line could only partly be drawn, and this portion is 

 composite, taken from both the anterior and posterior ends of the 

 specimen. Apart from the diphyllic external and two lateral saddles 

 shown in Fig. 2c, there are three more dij)hyllic saddles ; but the 

 remainder of the suture-line, apparently consisting of three more 

 saddles, cannot be clearly made out. The suture-line, then, differs 

 from that of the above specimen chiefly in having a more complex 

 and deeper external lobe and a more diphyllic first lateral saddle. 



Observations. — There is great resemblance in the suture-line and 

 apjjearance (of the smooth inner whorls) to the Callovian Phylloceras 

 subobtusiforme Pompeckj ^ from Alaska. But this form is a little 

 thicker, and apparently has an umbilical edge, since it is compared 

 with Phylloceras subobtusum Kudernatsch and Phylloceras Abichi 

 Uhlig. The fact that the ornament is not preserved prevents closer 

 comparison with Ph. isomorphum Gemmellaro,'^ which has similar 

 (but variable) dimensions. Also the suture-line of this form has 

 slenderer saddles and folioles. Since, however, the suture-line of 

 the earlier portion of the East African specimen shows, in this respect, 

 greater resemblance to Gemmellaro's figure than the last suture-lines 

 (a matter of preservation), this j)oint is less significant than the 

 larger umbilicus in the Sicilian species. 



Phylloceras trifoliatuni Neumayr,^ from the Bajocian of the 

 Carpathians, also comes close to the present form, but its suture-line 

 is characterized by a triphyllic first lateral saddle. Vacek ^ stated 

 that the specimen from San Vigilio (from which the suture-line 

 given by Neumayr in Fig. 2 was taken) was not identical with the 

 Hungarian Ph. trifoliatum and belonged to Ph. chonomphalum 

 Vacek of a different grou23. This jioint see2ns to have escaped 

 Prinz,'' whose otherwise unconvincing divisions within the genus 

 Phylloceras have not been adopted by the writer.^ Of the Bajocian 

 forms of Phylloceras described by Prinz, Ph. baconicum '' is very near 

 the present specimen, but its suture-line is more complex than the 

 one here figured (though taken from a larger specimen). 



The absence of constrictions and its general appearance 



^ " Jurafossil. au.s Alaska " : Verh. Russ. Kais. Mineral. Ges. St. Petersb., 

 ser. II, vol. xxxviii. 1900, p. 247, pi. vii, fig. 1. 



- Faune Giur. & Lias., pt. i, 1872, p.X pi. i, fig. 1 ; pt. v, 1877, p. ISO, 

 pi. xix-, fig. 16. 



^ " Jurastudien," ii : loc. cit., p. 309, pi. xii, figs. 2, 3. 



^ " Ub. Fauna Ool. Cap San Vigilio " : Abh. k.k. R.A., Vienna, vol. xii, 

 1886, p. 69. 



^ " Die Fauna alt. Jurabild. N.O. Bakony " : Mitt. Jalirb. Ungar. Geol. 

 Anst., vol. XV, 1904, p. 40. 



" Jullien's (C. R. somm. Soc. Geol. France, June 19, 1911) divisions and 

 speculations on sexual dimorphism among Phylloceras also seem unfounded. 



■^ lb., p. 38, pi. xxvii, fig. 2. 



