Jurassic Mollusca from Arabia. 13 



In its general form the Arabian species possibly closely 

 resembled the form which Dacque * has described (as Nauti- 

 lus ennianus) from Somaliland from beds which he regards as 

 of Kimeridgian age. The Somaliland fossil has a similar 

 subangular- margined periphery, but its ornaments are 

 unknown. 



The concave peripheral area of Nautilus giganteus — a 

 species sometimes regarded f as a synonym of J. de C. 

 Sowerby's Nautilus hexagonus- — described by d'Orbigny \ 

 from the Lower Oxfordian, but recorded § also from beds of 

 Lower Kimeridgian age, seems to distinguish that species 

 from both the Arabian and Somaliland forms. 



Of the species recorded from the Jurassic rocks of Cutch, 

 the Arabian form may be compared with both Nautilus 

 kumagunensis, Waagen ||, and Nautilus wandaensis, Waagen ^[ ; 

 from the former, however, it seems to be distinguished by its 

 coarser lines of growth and apparently more robust form, and 

 from the latter by its probably narrower and more sharply 

 defined periphery. On the whole, however, it seems to come 

 nearer the latter, but unfortunately in that species the test, 

 which is very well shown in the present specimens, is incom- 

 pletely known. Nautilus kumagunensis occurs in the upper 

 region of the macrocephalus-beds, whilst N. toandaensis occurs 

 in the Dhosa Oolite in association with Aspidoceras per- 

 armatum. Nautilus i&andaensis has also been recorded, in 

 association with Perisphinctes, Macrocephalites, indeterminable 

 fragments of Belemnites, and a new species of Rhynchonella, 

 from Mtaru in German East Africa, from rocks regarded as 

 of the same age as the Dhosa Oolite ** of Cutch. 



The flat, sharply-defined periphery, with its subangular 

 margins and feeble longitudinal sulcus near the margin, the 

 slight depression of the outer part of the lateral area, and the 

 direction of the lines of growth in the Arabian example 



* E. Dacque", Beitr. zur Paliiont. u. Geol. Oesterr.-Ungarns, &c, 

 Bd. xvii. Heft 3 & 4, p. 144, pi. xvii. fig. 5. 



t See A. H. Foord, Cat. Foss. Ceph. Brit. Mus. pt. 2, 1891, pp. 235- 

 236. 



% A. D. d'Orbigny, Pal. Fran?., Terr, jurass. vol. i. 1842, p. 163, 

 pi. xxxvi. 



§ A. Etallon, " Letbtea Bruntrutana, &c," pt. 1 (Neue Denkschriften 

 der allgemeinen Scbweizeriscben Gesellscbaft fur die gesanimten Natur- 

 wissenschaften, Bd. xviii.), 1861, p. 74, pi. i. fig. 2. 



|| W. Waagen, ' Jurassic Fauna of Kutcb ' (Pal. Indica), vol. i. 

 Cephalopoda, pt. 1, 1873, p. 19, pi. iii. furs. 1 a, b. 



% W. Waagen, op. cit. pt. 1, 1873, p. 17, pi. iv. figs. 3 a, b. 

 ** A. Tornquist, " Fragmente einer Oxfordfauna von Mtaru irn Deutscb- 

 Ostafrika, nach dem von Dr. Stublmann gesammelten Material," Jabrb. 

 Hamburgiscbeu Wissenscb. Anstalten, Jahrg. x. (1892), p. 281. 



