104 



In D'Orbigny'e figure of thepeptiim of ^. Velledcs, the siphonal saddle (or 

 small saddle through which the siphon passes) is represented as lanceo- 

 late, with an entire mai-gin ; whereas the corres])onding saddle in A. 

 ramosus is figured by Meek as three lobed or twice incised at the summit, 

 and this difference might be, and indeed has been, looked upon as of 

 specific importance. The value of this character, however, is entirely 

 negatived by the fact that Pictet and Stoliczka both repi-esent the siphonal 

 saddle of A. Vdledce as three lobed or twice incised at the apex, and their 

 figures of the septum of that species agree precisely with Meek's drawing 

 or tracing of the septum of A. ramosus. The plates of Ammonites in the 

 first volume of the " Paleontologie Suisse" shew that the shape of the 

 siphonal saddle varies con:*iderably in different individuals of the same 

 species, and suggest grave doubts as to the validity of distinctions which 

 ai'e founded only on supposed diti'erences in this part of the septa*. 



AjyiMONiTKS Selwynianus. (N. Sp.) 

 Plate 13, figures 1 and la. 



Shell somewhat compi-essed at the sides and rounded on the periphery; 

 umbilicus extremely smal I ; surface of the test marked by fine, flexuous 

 sti-ise, which curve forwards and form long beak-like processes on the 

 siphonal edge; cast impressed by distant, periodic grooves, which cui've 

 in the same direction as the striae on the test. 



"Whorls strongly involute, nearly the whole of the inner turns being 

 concealed ; outer volution moderately inflated, thickest near the middle 

 of the sides and slightly depressed round the umbilical opening. Umbil- 

 icus rather less than one-tenth of the greatest diameter of the shell, very 

 deep, with a rounded margin and almost perpendicular sides. Aperture 

 ovate, wider above than below, and very deeply emarginate for the 

 reception of the previous volution. Measured along the median line, 

 where the emargination is deepest, the width of the aperture is greater 

 than its height, but outside of the emargination the entire height of the 

 whorl or aperture is much greater than its width. 



Test ornamented by faint and very delicate, flexuous striations, 



*0n pp. 43-45 Of the pressen'^ Volume, Ave Ammonites f om the Queen Charlotte I^^lands 

 were described under the name A. fiUcinctns, and these were sep uated trom A. Sacya (p'orbes) 

 on precisely the sume grourds as those which were relied upon by Meek for distinguishing his 

 A. ramosus trom A l^elledce—Wz , a hupposed difference in the shipr of tlielr blphonal saddles. 

 At ihe time tiiat A. filkinctus was desi rlbed, the writer had not access to the " Pa :6Dntologie 

 Suisse," and con-equentiy was not then aware that the shape of the siphonal saddles was 

 variable In different specimens of the same Ammonite ; but tije -vork referred t(rhas since been 

 added to tue L'brary ol tlie Survey, and. It Is aow almo&t certain that A.filkittctui Is Weutlcal 

 WltAX.Ja<;yifc 



