Yol. 69.] JTTKASSIC AMMONITES EROM JEBEL ZAGHTTAN. 561 



If then, despite this close agreement in dimensions and all 

 details, I do not entirely identify my specimen -with the type, it is 

 on account of its bad state of preservation. 



The ammonite which M. Neumayr figures and describes * as 

 Perispliinctes curvicosta (Opp.), but belongs, according to Siemi- 

 radzki, to the group of P. caroli Gemm., shows much resemblance 

 to the form here described. Its section is, however, wider ; the costae 

 are more strongly sigmoidal and rursiradiate ; there are parabolar 

 knobs; and altogether the ammonite has still much more affinity 

 with the typical Grossouvrice than with the form here described, 

 and has probably been excluded from that subgenus only on account 

 of its large size. It may be considered a transitional form from the 

 Grossouvria-curvicosta group to the groups of Perispliinctes caroli 

 and P. orion, the latter including the ammonite here described 

 with initial Perisphinctate costation of a more prorsorectiradiate 

 character and much larger dimensions. 



With the true Perispliinctes curvicosta (Opp.) Siem., 2 and espe- 

 cially P. curvicosta (Opp.) in Waagen, 3 which has a very irregular 

 ornament and rounded section, there is, therefore, correspondingly 

 less agreement. 



Dr. Till figures a Perispliinctes cf. curvicosta (Opp.), 4 which also 

 bears a certain resemblance to the form here described ; but in 

 this the costation is similarly rursiradiate and the umbilicus is 

 too narrow. Of the other forms figured by the same author, 

 only P. villdnyensis Till and P. leptoides Till somewhat resemble 

 my specimen. In the former the umbilicus is narrower, and the 

 primary costse are fewer than in my specimen. P. leptoides has 

 parabolar knobs and a section too wide near the periphery. 



With the other ammonites included in the groups of P. caroli 

 and P. orion, my specimen is less closely comparable. 



(3) UPPER JURASSIC. 

 Genus Phyllocekas Suess. 



PhYLLOCERAS Cf. MEDITEEEANEUM Neum. 



1898. A. de Kiaz, ' Description des Ammonites des Couches a Peltoceras trans- 

 versarium de Trept (Isere) ' pi. xvi, figs. 9-10 & p. 40. 



Seven out of fourteen Phyllocerates belong to this form, which 

 seems fairly common at Sidi Bu Gubrin. These agree very closely 

 with the figures given by A. de Biaz ; and the form is, indeed, 

 easily recognized by its comparatively-wide umbilicus, its five 



1 ' Cepbalop, Fauna d. Oolithe von Balin ' Abhandl. K.K. Geol. Eeichsanst. 

 vol. v (1871) pi. xii, fig. 2 & p. 34. 



2 ' Monogr. Bescbreib. d. Arnmonitengattung Perispliinctes ' Palasonto- 

 grapbiea, vol. xlv (1898) p. 96. 



3 ' Jurassic Fauna of Kutcb ' Pal. Indica, ser. 9, vol. i (1873) pi. xxxix, 

 figs. 4-6 & p. 169. 



4 'Amm. Fauna des Kelloway von Villany' Beitr. Palaont. Geol. (Esterr.- 

 Ung. vol. xxiv (1911) pi. (iv) viii, fig. 5. 



