Vol. 69.] JURASSIC AMMONITES FROM JEBEL ZAGHTTAN. 571 



form. Their section is broader than high, however, and this 

 distinguishes them equally from my ammonite. A. de Biaz's 

 forms may be possibly identified with Perisphinctes sp. nov. aff. 

 birmensdorfensis, quoted by Siemiradzki 1 ; but the number of costse 

 in the latter seems to be at least fifty at a diameter of 58 mm. 



Perisphinctes (Grossouvria) cf. densicosta Gemmellaro. 



1877. G. G. Gemmellaro, ' Fanne Giur. & Liass. della Sicilia ' p. 200 & pi. xvi, 



fig. 7. 

 1898. J. vou Siemiradzki, op. sitpra cit. Palajontographica, vol. xlv, p. 89.' 



A fragment shows the oblique diehotomous costae as in the type ; 

 but the secondaries seem to be more regularly bifurcating, and the 

 two branches pass across the periphery without the strong forward 

 bend. The section also is probably slightly flatter at the sides, and 

 these form more of an angle at the umbilical border. 



The type comes from the low-er beds of the acanihicus zone of 

 Sicily. 



There does nob seem to be any Argovian form with which my 

 specimen might be more closely connected; but, since I possess only 

 a fragmentary specimen, comparison becomes both difficult and 

 unreliable. 



Perisphinctes (Biplices) kobelti JNTeumayr. 



1885. M. Neumayr, ' Geogr. Verbr. d. Jurafovm.' Denkscbr. K. Akad. Wissensch. 



Winn, vol. 1, p. 82 (138) & pi. i, fig. 1. 

 1907. L. Pervinquiere, ' Etudes de Paleontologie Tunisienne : I — Cepbalopodes 



des Terrains Secondares ' p. 22 & pi. i, fig. 5. 



Two specimens from Sidi Bu Gubrin seem to agree well with the 

 figures and descriptions given for this form. They show the wide 

 umbilicus of about 50 per cent, of the diameter, a section which is 

 slightly broader than high, and two very deep constrictions on the 

 last whorl. The number of costse (fifty-five) and their continuity 

 across the venter seem to show that my ammonite is even nearer 

 jSTeumayr's type than the specimen figured by Pervinquiere. 



One of the specimens, which seems to have suffered in earth- 

 movements, might possibly belong to an allied Simocerate form, as 

 its periphery is not well preserved. 



As I mentioned in the first part of my paper, I am not at all 

 satisfied that the age of this form is ' certainly Tithonian.' Le Mesle 

 has found it with ' Oxfordian ' fossils, and its association at Sidi 

 Bu Gubrin with ammonites the great majority of which belong to 

 the transversarius zone does not confirm Pervinquiere's view. 



TJhlig considers these forms of the tiziani group to be true 

 Perisphinctes ; but, since he omits to state his reasons for not 

 accepting Siemiradzki's classification, and, further, since he does 

 not seem to have made a detailed study of the early Perisphinctoids, 

 I prefer to leave the form here described in the subgenus Biplices 

 v. Sutn. 



1 'Monogr. Bescbreib. der Ammonitengattung Perisp>hinctes' Palceonto- 

 grapbica, vol. xlv (1898) p. 87 : Ammonites colubrinus (pars) Quenst. 



