2i6 Tilompson : The Ammonites ealled A. serpentinus. 



another, especially A. serpentinus and A. mulgravius, as the 

 accompanying- plates alone will show. 



Mr. Buckman wrote in the ' Geological Magazine ' for 1887, 

 that Oppel, in his ' Juraformation,' p. 243, noticed the blunder 

 and kept both species (falcifer and serpentinus) distinct ; that 

 Dr. Haug, in his ' Beitrage Monog.', 1885, drew pointed atten- 

 tion to the fact of falcifer having been generally figured for 

 serpentinus ; also that Dr. Haug separated Am. serpentinus 

 totally from Am. falcifer, placing the former in the group of 

 bifrons, and so in Hyatt's genus Hildoceras. Both Oppel and 

 Haug give mulgravius as a synonym of falcifer. 



Below wdll be found Sowerby's own description of his 

 falcifer, Buckman's description of Strangwaysi for those 

 who have never seen the type ; and finally, a contrast of the 

 characters of Reinecke's serpentinus and of the most common 

 Yorkshire type, which former collectors called mulgravius 



It will, however, be seen from the plates and Mr. Buckman's 

 comparison above, that it is not the typical mulgravius of Young 

 and Bird, for that does not for one thing possess those coarse 

 broad ribs on the outer whorl. 



The following is Sowerby's description of falcifer. (' Min. 

 Con.', Vol. III., p. 99) Spec. Char. : — ' Discoid ; radiated ; 



(a) Section of last whorl of Sowerby's ^falcifer.' (Natural size.) 

 [h) Section of last whorl of the adult specimen figured on plate XIV. 

 nat. size). 



(Both these drawings have been very slightly reduced in reproduction). 



radii curved and suddenly bent in the middle ; inner volution 

 half exposed ; margin convex, carinated ; w^horls convex on 

 their sides ; aperture elliptical. 



' The diameter is little more than twice the length of the 

 aperture. The radii are numerous and close together ; as they 

 diverge from the centre they turn a little forward, then bend 

 suddenly back, and afterwards proceed in regular semi-circles 



"* Naturalis t , 



