16 Messrs. R. B. Newton and G. C. Crick on some 



absence of these same characters prevents a full comparison 

 with the Niti examples, which EL F. Blanford referred to 

 Ammonites torquatus * and A. biple.vf, two forms very 

 closely allied, if not identical, the only characters by which 

 that author distinguished the two forms being the thicker and 

 more depressed whorls of the former, accompanied by a slight 

 notching of the ribs in the median line of the periphery. He 

 did not figure A. torquatus, but figured two examples as 

 A. biplex. Of these, the specimen depicted in pi. xi. fig. 1 a J 

 more closely resembles the Arabian form, especially in the 

 coarseness and direction of its ornaments, but being a more 

 widely umbilicated shell, its outer whorl bears a greater 

 number (55) of principal ribs than that of the Arabian fossil. 



Compared with Waagen' s figure § of Perisphinctes martelli, 

 Oppel, from the Kuntkote Sandstone, the measurements of 

 which agree fairly well with those of the Arabian specimen, 

 the latter possessed coarser and more curved ornaments, and 

 apparently had more inflated sides than the Indian form ; 

 further, the bifurcation of the ribs appears to have been nearer 

 the margin of the periphery in the Indian than in the Arabian 

 form. 



Another Indian form with which the Arabian specimen 

 may be compared is Waagen's Perisphinctes virguloides ||, 

 but compared with Waagen's figure (pi. xlix. figs. 1 a, 1 b) 

 the Arabian fossil is more narrowly umbilicated and its ribs 

 are less numerous per whorl and more forwardly-directed in 

 crossing the lateral area. In Cutch, Waagen's species is 

 restricted to the Kuntkote Sandstone. The Arabian fossil 

 agrees still more closely with Pavlow's figure of a specimen, 

 which he refers to Waagen's species, from the zone of 

 Aspidoceras acanthicum from the East of Russia^. 



It also closely resembles de Loriol's figure** of Perisphinctes 

 eupaJus (d'Orbigny) from the zone of Oppelia tenuilobata of 

 Oberbuchsitten (Soleure) ; its relative dimensions are about 



* II. F. Blanford, in J. W. Salter and H. F. Blanford, Palseont. Niti, 

 18G5, p. 80. 



t H. F. Blanford, op. cit. p. 79, pi. xi. figs. 1 a, b, c, pi. xii. figs. 1 a, b, c. 



X Now in British Museum collection, register no. C. 5033. 



§ W. Waagen, op. cit. pt. 4, 1875, pi. lv. figs. 3 a, b. 



|| W. Waagen, op. cit. pt. 4, 1875, p. 203, pi. xlvii. figs. 4 a, b, pi. xlix. 

 figs. 1 a, b. 



^[ A. Pavlow, "Les Ammonites de la zone a Aspidoceras acanthicu»i 

 de Test de la Russie," Mem. Com. G6ol. St. Petersbourg, vol. ii. no. 3, 

 188G, pp. 28 & 85, pi. via. figs. 3 a, b. 



** P. de Loriol, " Monographie pal^ontologique des couches de la zone 

 a Ammonites tenuilobatus (Badener Schichten) d'Oberbuchsitten et de 

 "VVengen (Soleure),'' pt. i., 1881 (Mem. Soc. Fal. Suisse, vol. vii.), pi. iii. 

 figs. 2, la. 



