12 JURASSIC FAUNA. 



d'Orbigny's Ammonites bullalus; a comparison of the figures leads to the conclusion 

 that they represent dififerent species. All I wish to state here is, that the form from 

 Baluchistan certainly differs from Quenstedt's Ammonites bullatus as regards the 

 general shape, and that I am doubtful as to whether the relationship of that species 

 with the form from Kutch is so close as Professor Waagen supposes it to be. 



2. Genus: MACROGEPHALITES.Sutn. 



Macbooephalites macrgcephaltjs, Schlotheim. PL VII, fig. 1-la, PI. VIII, 



Plate IX, fig. 1. 



1875. Stephanoceras macrooephalns, Waagen, Palseontologia Indica, Jurassic Fauna of Eutch, Vol. I, p. 10&, 

 PI. XXV, PI. XXVII, fig. 1, a. b, (non o) PI. XXXIII, fig. 5. 



Dimensions. I. II. 



Diameter of tlie sbell 2ia 116 



„ of the nmbilicns 32 17 



Height of the last whorl from the umbilical sntnre . . . . 123 64 



„ „ ,, from the preceding whorl ... 70 (?) 50 



Thickness of the last whorl (F) (P) 



The shell consists of rather compressed moderately high whorls which so com- 

 pletely overlap each other that only a very narrow umbilicus remains. The sides 

 are flat and slope from the umbilical edge towards the rounded siphonal side. As 

 the whorls are laterally compressed and increase only slowly in height the cross- 

 section is elliptical in shape. 



The sides are covered with numerous, very regular fine polytomous ribs, of 

 which the stems are always effaced in the neighbourhood of the umbilicus, the ribs 

 pass in a straight line over the siphonal side, where they follow each other at 

 equal intervals, which are somewhat broader than the ribs themselves. On large 

 specimens the ribs completely disappear on the body-chamber. The body-chamber 

 is apparently not large, its length being about three quarters of the last whorl. 

 Towards the aperture the body-chamber deviates from the regular spiral, the um- 

 bilicus becoming slightly wider while the mouth is contracted. 



Sutural line very indistinct. 



Locality and stratigraphical position. — Mazar Drik ; JBolyphemus-\im&&ioiaei. 



Bemarks. — Professor Waagen mentions that the chief variations of this species 

 consist in the differences of the transverse diameter of the whorls and the number 

 of ribs. The specimens under examination are too ill-preserved to allow of any de- 

 finite statements as to the number of ribs, but as regards the transverse diameter it 

 seems that they are generally somewhat more compressed than the specimens figured 

 by Professor Waagen. I have before me his originals, and a careful comparison of 

 the two forms shows that the Baluchistdn forms have less inflated whorls than those 

 of Kutch, the cross-section is therefore slightly different, being more compressed 

 in the former than the latter ; on the other hand the general shape of the shell, the 



