298 M. Bullen Neu-tou — Marine Fossils from Mekran Coast. 



' Mekran Group,' referred to in the foregoing literature, but, 

 unfortunately, I have not been able to trace them either in the 

 Museum of the Geological Society or in the British Museum, and 

 I can only conclude that the}^ may possibly be among the Indian 

 Survey collections at Calcutta. 



As it seems fairly apparent that no previous writers have called 

 attention to the occurrence of these fossiliferous nodules, it is to be 

 hoped that the present communication may be of sufficient interest 

 to induce the authorities of the Indian Geological Survey to re- 

 examine the rocks of the Mekran coast, with the view of discovering 

 the exact position of the bed whence the nodules were derived, sO' 

 that its relationship to the other deposits of the Mekran Group could 

 be properly established. 



DESCRIPTION OF THE SHELLS. 



Lamellibranchia. 



Arca Blanfordi, n.sp. (PI. XVI, Fig. 5.) 



Shell subquadrate, ventricose, arched, with an angulate, truncated, 

 deep posterior side, the anterior area being rounded and oblique y 

 umbones subcentral, rounded, sti'ongly incurved ; surface radiately 

 ribbed and sulcated ; ribs about 27, with depressed summits, angu- 

 lated margins ; surface transversely striated. 



Dimensions. — Of moderate-sized right valve : umbono-ventral, 45 ; 

 antero-posterior, 45 ; diameter of valve, 20 mm. 



In its contour and general radiate appearance this species resembles 

 Arca rhomhea of Born, found oif Ceylon and the Chinese seas, and 

 which also occurs in the raised beach deposits of Karachi, India. It 

 differs, however, in the valves being more rounded and arched, 

 besides showing an absence of nodulous ornamentation on the ribs, 

 which is especially developed on the anterior half of A. rliombea. 

 The specimen figured is taken from a wax squeeze of a fairly well- 

 preserved right valve found in one of the nodules, showing the more 

 elevated region partially covered with cost^, the ventral area being 

 stripped of the shell, thus exhibiting an impression of the extremely 

 fine and close longitudinal striee which adorn the internal surface of 

 the valve, and which extend to within a short distance of the margin. 



This shell is named in honour of Dr. W. T. Blanford, CLE., 

 F.R.S., a former Director of the Geological Survey of India, and one 

 of the earliest writers on the geology of the Mekran Coast. 



Examples. — Only three or four specimens in the collection. 



Mactra mekranensis, n.sp. (PI. XVI, Figs. 6, 7.) 

 Shell subtriangularly ovate, cordiform, moderately convex, obtusely 



angulate posteriorly ; umbones nearly central ; sculpture consisting. 



of narrow, depressed, smooth, concentric banding of equal width, 



each band separated by an extremely narrow sulcation. 



Dimensions. — Eight valve : umbono-ventral, 40; antero-posterior, 



47; diameter, 10 mm. 



The specimen referred to this form is represented by a right valve, 



being mainly an internal cast, yet retaining a small patch of original 



