47 



inches in the greater, and '53 inch in the small diameter), 

 of an individual which, judging from an impression left on 

 the matrix, must have been not less than five inches across ; 

 consequently the structure above given is only that of an 

 immature individual. 



As there is no well defined distinction between the genera 

 Scaphites and Ammonites, excepting the form of the outer or 

 body whorl, I have only referred this and the following 

 species provisionally to the latter genus, until entire speci- 

 mens can be seen. 



Ammonites Newberryanus. — Oval discoidal, rounded on 

 the dorsum ; umbilicus broad, conical in form, less than one- 

 third the greater diameter of the shell ; volutions five and 

 a half or more, slightly compressed laterally, and sloping a 

 little from near the ventral side towards the periphery, in- 

 ner ones more than half hidden. Surface ornamented by 

 distinct rounded costee, which occasionally bifurcate near 

 the umbilicus, and about half way across towards the dor- 

 sum. The depressions between, generally about equal the 

 costas in size, but at intervals of six or seven times to each 

 turn, one of them forms a kind of deep constriction ; a sin- 

 gle row of rather distinct transversely elongated nodes sur- 

 round the umbilicus. 



The septa are deeply divided into seven lobes on each 

 side, which rapidly diminish in size towards the umbilicus. 

 Dorsal lobe a little larger than the superior lateral lobe, and 

 having on each side three principal branches, the two ter- 

 minal of which are larger than the others, and each again 

 irregularly divided into two or three subordinate branches 

 with more or less sharp digitations. Dorsal saddle deeply 

 divided at the extremity into two subequal parts, and having 

 on the ventral side below three, and on the dorsal two, ir- 

 regular alternating lateral branches ; the two terminal 

 divisions are much larger than the others, and each tripar- 

 tite, with the upper subivisions bifid, and all more or less 



