Vol. 69.] JURASSIC AMMONITES FROM JEBEL ZAGHEAN. 565 



Phyllooeras cf. isotypem (Benecke). 



1865. E. W. Benecke, ' Ueber Trias & Jura in den Siidalpen ' Geogn. Pal. Beitr. 



p. 184 & pi. vii, tigs. 1-2. 

 1871. M. Neumayr, ' Phjlloceraten des Dogger & Malm ' p. 314 & pi. xiii, fig. 3. 

 1896. M. Canavari, ' Strati con Aspidoceras acanthicum del Mte. Serra' p. 32. 

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



des Terrains Secondares' p. 11. 



One small ammonite in the collection seems to be comparable 

 •with Benecke's form. It has tbe flattened sides, deep umbilicus 

 bordered by steep walls, and radial striation at the periphery : 

 the section, however, is not rounded-quadrate, but more elliptical. 

 Its thinness excludes it also from the var. appenninkum Canav. of 

 Ph. isotypum (Ben.). 



A larger specimen has the somewhat broadened venter of 

 Benecke's form, but the umbilicus is smaller and fairly shallow, 

 although it may only have been worn down. It resembles in this 

 respect Phi/lloeeras serum (Oppel) ; but the latter ammonite is 

 mucli thinner, especially near the periphery. 



This ammonite is very common in the ' acanihicus ' zone of the 

 Alps and Sicily, and Pervinquiere has recorded it (although not 

 with certainty) from Jebel Ben Saidan in Tunisia. I have 

 not come across any Argovian Phylloceras with which my speci- 

 mens cnuld be compared; but, in view of the fact that they were 

 collected together with a large number of transversarius-zone 

 fossils, I may mention that there is a possibility of the first 

 specimen representing the inner whorls of Ph. plication Neumayr. 

 It has the peripheral ornament, but differs apparently in the 

 umbilicus. In any case, it must be remembered that it is a young 

 specimen, and that the other ammonite, as well as Phylloceras 

 cf. saxonicum Neum., described previously, are worn specimens, so 

 that their attribution to the ' acanihicus' zone is doubtful. 



According to Dr. Pompeckj, 1 Ammonites heterophyllus albus 

 'Quenstedt, 2 from the bimammatum zone of Laufen, differs from 

 Benecke's type only in having a narrower umbilicus and less flat 

 ■sides. 



Genus Sowerbyceras Par. & Bon. 



SOWI'RBYCERAS PROTORTISELCATUM (Pomp.). (PI. LIII, figS. 2a-2c.) 



1893. J. P. Pompeckj, ' Beitrase zur Revision der Ammoniten d. Schwabischen 



Jura' pt. 1, p. 53 & pi. ii, tigs. 1-2. 

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



des Terrains Secondares ' p. 15. 



This easily-recognizable ammonite is exceedingly common at 

 Sidi Bu Gubrin, and I can identify twenty-one specimens with 

 Pompeckj's types, whereas only two specimens appear to belong to 

 a different form of /Sowerbyceras. They are all casts, and the 

 measurements of eleven forms are as follows : — 



1 'Beitr. z. Revision d. Amnion, d. Schwabischen Jura' pt. 1, 1893, p. 28. 



2 ' Arnmuniten d. Schwabischen Jura' 1888, p. 901 & pi. xcvii, fig. 7. 

 <Q. J G. S. No. 276. 2 p 



