Genus Oxh\iox()^QB of d* Orhigny. 445 



of the British Museum, aided bj sections made by Dr. G. J. 

 Hinde, I am in a position to give the following description of 

 a genuine specimen of Orbitoides media from the Upper 

 Chalk of Maestricht : — 



This is circular, slightly wavy, depressed, conical on one 

 side, where it ends in a slight central papillary projection 

 corresponding to a gentle depression on the opposite side, 

 which is otherwise slightly convex, granular on both sides, 

 the granules often presenting an indistinctly sinuous linear 

 arrangement towards the circumference. Internal structure 

 consisting of a central plane, in which the cells or chambers 

 in a fresh state appear in a horizontal section to have been 

 circular and situated respectively in the interstices of inter- 

 crossing centrifugal lines, which, radiating from the centre in 

 opposite directions, thus present the " engine-turned " pattern 

 to which I have above alluded, and show how the first- 

 formed or central cells become smallest and the circum- 

 ferential ones the largest ; while in the vertical section the 

 same circumstances cause the central plane to be thinnest in 

 the centre and widest at the circumference, where apparently 

 the layers of cells, by running into each other, cause the 

 divisions of the central plane to present a series of curved 

 cylinders, whose convexities are directed outwards. Central 

 plane covered in on each side by a convex crust composed 

 of columns of vertically compressed cells, intermingled with 

 conical columns of more consolidated whitish shell-substance, 

 whose obtuse ends form the granules of the surface and whose 

 pointed ones appear to reach the angles of the interstices in 

 the central plane. Size of specimens varying a little under 

 8-24ths inch in diameter and 2-24ths in thickness in thecentre, 

 including the papillary projection. 



Log. Upper Chalk of Maestricht. 



Ohs, The above description is quite sufficient to recognize 

 the fossil, but would have been more satisfactory if the fossili- 

 zation had been more crystalline and compact. No. of speci- 

 mens " P. 1490." 



Such are the characters of the little discoid fossil from 

 Maestricht, and they are fundamentally the same as those 

 presented by the large specimens of Orhitolites Mantelli from 

 Nal, in the province of Jhalawan, to which I have just 

 alluded. Dr. Cook states, in his " Topographical and 

 Geographical Sketch of a portion of the Province of 

 Jhalawan &c., or northern part of the Tableland of Beloochi- 

 stan " (Trans. Med. and Phys. Soc. Bombay, no. vi. new ser. 

 1861, p. 71 ; whence the subjoined diagrammatic figure 

 is taken), that " this limestone in some places is crystalline 



