Jurassic Mollusca from Arabia. J 7 



the same, so far as they can be compared with the Arabian 

 specimen, although the measurements of the figure do not 

 quite agree with the dimensions given by de Loriol (p. 16) * ; 

 but its ornaments appear to be somewhat finer and fewer, 

 de LorioPs example having 47 principal ribs in the outer 

 whorl, whereas the Arabian fossil has only 42 or 43. 



This specimen, then, seems to find its nearest ally in 

 Perisphinctes torquatus, w r hich occurs in the Katrol Group 

 in Cuteh in beds which are referred to by Siemiradzki f as 

 Lower Kimeridgian ; at Niti and Spiti in the Himalaya; 

 and, according to Siemiradzki, also in the zone of Oppelia 

 tenuilobata in Poland, and probably also in Swabia. 



A crushed specimen, about 34 mm. in diameter, exposed 

 on the surface of a small piece of limestone, appears to be 

 referable to this same species. 



Loc. Valleys between the villages of Al-Kura and Sarama, 

 about 15 miles N.E. of Dihala. 



Perisphinctes cf. subdolus, Fontannes, 



(PI. II. tig. 3.) 



1879. Perisphinctes subdolus, F. Fontannes, Description des Ammonites 

 des caleaires du Chateau de Crussol, Ardeche (Zones a Oppelia tenui- 

 lobata et Waage7iia beckeri), p. €1, pi. ix. fig. 3. 



1898, Perisphinctes subdolus, F. Fontannes ; J. v. Siemiradzki, Palseon- 

 tographica, Bd. xlv. Lief. 2 & 3, p. 153. 



Another species of the genus Perisphinctes, represented by 

 the crushed half of a specimen of about 83 mm. in diameter 

 and with the inner whorls obscured by matrix, bears some 

 resemblance in the character of its ribbing to Perisphinctes 

 subdolus, Fontannes, a rather common species in the zone of 

 Oppelia tenuilobata of Crussol (Ardeche) ; but it appears to 

 have been a more widely umbilicated shell with relatively 

 narrower (*". e. less high) whorls, for the diameter of its 

 umbilicus at about its greatest diameter ( = 1) appears to be 



* The measurements given bv de Loriol are : — greatest diameter 78 mm. ; 

 width [height] of last whorl, in proportion to the diameter, - 37 ; thick- 

 ness of last whorl, in proportion to the diameter, 0-34 ; diameter [width] 

 of umbilicus, in proportion to the diameter, 037. From these dimensions 

 it would appear that the width [height] of the last whorl and the diameter 

 of the umbilicus were equal, but such is not the case in de Loriol's figure. 

 Our dimensions of the figure are: — greatest diameter 79-5 mm. (1); 

 height of last whorl 27 (0 - 34) ; thickness of last whorl 28 (0-35) ; width 

 of umbilicus 33-5 (0-42 j. 



f J. v. Siemiradzki, ' Palaeontographica,' Band xlv. Lief. 4 & 5, 1898, 

 p. 264. A. de Lapparent divides the Katrol group into two parts, and 

 regards the Lower part as of Sequanian age and the Upper as of Kime- 

 ridgian age (' Traite de GSologie,' 5th ed. 1906, vol. ii. pp. 1243 & 1255). 



Ann. & Mag. N. Hist. Ser. 8 Vol. ii. 2 



