16 JURASSIC FAUNA. 



from others by its larger umbilicus, and the curve of the stronger ribs on the 

 siphonal side. 



Unfortunately the Baluchistan specimens are too much distorted to allow of 

 the features of the umbilicus being studied, but so far as can be seen, this form 

 certainly differs by a wider umbilicus from the other species here described. A 

 much better distinguishing feature, however, is the character of the ribs, which are 

 well marked and bend slightly forward. I must however state, that owing to the 

 bad state of preservation of the Baluchistan specimens, it would have been impossible 

 to identify them with this species, had I been unable to compare them with Professor 

 Waagen's original. This specimen, which represents a somewhat larger shell than 

 any of those under examination, seems to differ by somewhat stronger ribs and a 

 slightly flattened siphonal side ; but considering that the flattening of the siphonal 

 side does not take place until the beginning of the last whorl, I consider this a 

 character which can only be noticed in specimens which have attained a certain 

 size. On the other hand, it can be seen that the ribs become stronger with increas- 

 ing size, and that the smaller specimens from Baluchistan must necessarily have 

 finer ribs. It must also be mentioned that these specimens prove that the strength 

 of the ribs is seriously influenced by the weathering, and that originally the ribs 

 were stronger than they are now. 



Macrocephalites lamellostjs, Sowerby, sp. PI. VII, fig. 3-3a. 



1875. Stephanoceras lamellosum, Waagen, Palseoatologia Indica, Jurassic Fauna of Kutch, Vol. I, p. 123, 

 PI. XXXIII, fig. la, b. 



Dimensions,, 



Diameter of the shell , no mm. 



„ of the umbilicus . • . • 20 , 



Height of the last whorl from the umhilical suture f .... 50 



,1 u » from the preceding whorl 32 „ 



Thickness of the last whorl 50(?) 



The shell consists of slightly inflated and flattened whorls which almost com- 

 pletely envelope each other, thus leaving a narrow umbilicus. The' whorls are rather 

 low and increase in size but slowly ; the sides are almost flat and slope only slightly 

 near the siphonal side. The cross-section is a flattened ellipse. The sides are 

 covered with very strong, sharp and high ribs which begin at the umbilical edge and 

 run in a straight line towards the siphonal side ; at a point somewhat below the 

 middle of the height they divide into two or three branches of nearly the same 

 strength as the original stem ; these bend imperceptibly forward and pass at equal 

 intervals over the siphonal side. 



One specimen shows part of the inner whorls, which are covered with rather 

 fine ribs distinctly inclined forward on the siphonal side. 



Sutural line very indistinct. 



Body-chamber not preserved. 



Locality ani stratigraphical position.— Mazav Drik; Polpphemus-limestone, 



