574 me. l. f. spath on [Dec. 1 913, 



measuring 36 mm. in diameter, agrees with De Biaz's figure 

 in the obliqueness of the costation and constrictions, the flattened 

 sides, and the distinct umbilical rim. Unfortunately, the ammonite 

 is worn, and therefore the identification must remain doubtful. 



Another larger ammonite, 55 mm. in diameter, has its outer 

 whorl somewhat worn, but seems to agree in all details (except in 

 its thin section) with the ammonites figured by A. de Biaz in his 

 pi. iii as P. plicatilis Sow. 



In section, the specimen would agree more with P. olliqueplicalus 

 Waagen, as figured in Siemiradzki's pi. xxii, fig. 23 a and text- 

 fig. 2, p. 84. But the costation is not oblique enough here. 



The ammonite figured by De Biaz as P. cf. obliqueplkatus Waag. 

 (pi. xv, fig. 4) has the costae too distant; Siemiradzki regards it 

 as a new form ' P. bifurcatus,' but gives no figure of the section. 



Since my specimen is not well enough preserved, I prefer to 

 it with the equally indefinite Trept forms. Siemiradzki 

 unites all the four ammonites (which, it may be mentioned, differ 

 somewhat one from the other) with his '■plicatilis (Sow.) d'Orb.' 

 from the ' Lower Oxfordian,' and this makes me adopt the above 

 designation for the Argovian forms. 



Berisphinctes cf. coNvoLtJTUS (Quenst.). 



1888. F. A. von Quenstedt, ' Aramoniten d. Schwabischen Jura ' convoluti (pars) 

 pi. xciv, rigs. 20 & 43. 



1898. A. de Riaz, ' Descr. des Amm. des Couches a, Peltoceras transversarium 



de Trept (Isere) ' (P. convolutus Quenst.) p. 19 & pi. ix, rigs, oa 

 &5b. 



1899. J. von Siemiradzki, ' Monogr. Beschreib. der Ammonitengattung Peri- 



sphinctes ' Palteontographica, vol. xlv, p. 341. 



My small ammonite probably corresponds with the inner whorls 

 of a convolute Perispliinctes similar to that figured by De Biaz, 

 and seems to be somewhat intermediate between figs. 20 and 

 43 of Q,uenstedt's pi. xciv. It is very finely costate, with a 

 broad flat venter, forming an angle with the sides, and shows about 

 seven fine constrictions per whorl. At a diameter of 13-5 mm. 

 its thickness is about 55 per cent, and the height of the last 

 whorl 33 per cent., whereas De Biaz's form has, at an equal per- 

 centage of height, a thickness of only 46 per cent. ; but the diameter 

 is here much larger. 



Bervinquiere x mentions under Holcosteplianus cf. celsus (Opp.) 

 an ammonite from the red limestone of Jebel Ben Saidan, and this 

 seems to be distinguished from the form here described only by a 

 coarser costation and fewer and wider constrictions, if we assume 

 it to resemble in this respect the specimen figured by him from a 

 different locality. Spiticeras proteanum (Zitt. non Opp.) = Sp. celsum 

 (Opp.), also bears some resemblance in its inner whorls 2 to the 

 form now described ; but the different character of the constrictions 



1 ' Etudes de Paleontologie Tunisienne : I — Ceplialopodes des Terrains 

 Secondares' 1907, p. 41 & pi. ii, figs. 9-10. 



2 K. A. von Zittel & A. Oppel, ' Die Cephalop. der Stramberger Scbicbten ' 

 Pal. Mitt. Mus. K. Bayer. Staates, vol. ii, pt. 1 (1868) p. 90 & pi. xvi, fig. 2 b. 



