NAT7TIUD-E. 
47 
Trocholites ammonius, Conrad. 
1838. Trocholites ammoniiis, Conrad, Ann. Geol. Report, p. 119. 
lS4i?. Trocholites ammoniiis, Emmons, Geology of New York, pt. ii. 
p. 279, f. 3; p. 392, f. 1. 
1842. Trocholites, Utica trocholite, Yaniixem, Geology of New York, 
pt. iii. p. 57, f. 3. 
1847. Trocholites ammoniiis, Hall, Palaeontology of New York, vol. i. 
p. 192, pi. xl. A. If. 4 a-k ; ibid. p. 309, pi. Ixxxiv. if. 2 a-c. 
1888. Trocholites ammonius, Ami, Canadian Record of Science, yol. iii. 
No. 2, p. 105. 
Sp. Char. “ Discoidal ; volutions in the same plane, about four, 
rounded, slightly concave on the ventral side, gradually enlarging 
in size towards the aperture, which is slightly expanded ; surface 
marked by lamellose, irregular and oblique transverse striie or 
ridges, between and upon which are finer lamellose striae, covering 
the outer surface, and giving it a peculiar textural or netted appear- 
ance ; striae meeting in an arch upon the back ; septa direct, or 
slightly undulated on the dorsal [convex] side : outer chamber [body- 
chamber] large ; siphuncle ventral [internal] The peculiar 
character of the surface is produced by the numerous crowded edges 
of lamellae, which, in perfect specimens, are somewhat regularly 
undulating. Y^hen the shell is partially exfoliated, the textural 
character of the surface is destroyed, and it is only marked by fine 
oblique striae. The stronger striae are very variable, being some- 
times so prominent as to deserve the name of ridges, and at other 
times are only slight undulations ; while in many instances they are 
not at all developed, and the surface is marked only by the finer 
lamellose striae.” (Hall.) 
Remarks. Professor Hall states regarding the horizon of this 
species that it “ occupies a central position in the Trenton lime- 
stone, being unknown in the lower part, but passing upwards into 
the Utica slate, where it is of less frequent occurrence.” Mr. H. 
M. Ami records it from Murray Bay (Province of Quebec), and 
Whitby, Ottawa, and Collingwood (Province of Ontario), Canada, 
in the Utica shales. It does not appear to have been found above 
this horizon. Mr. J. F. Whiteaves ^ notes the occurrence in the 
Guelph Formation (Silurian) of Trocholites multicostatus, Whitfield, 
which he considers “ very closely allied ” to T. ammonius. 
Horizon. Trenton Limestone ( = Llandeilo). 
Locality. Middleville (Herkimer Co.), New York State. 
Represented in the Collection by two examples, presented by J. 
E. Lee, Esq., F.S.A., F.G.S. 
^ Palgeozoic Fossils (Geol. & Nat. Hist. Surv. Canada), vol. iii. pt. i. p. 36, 
pi. vi. ff. 1, 1 a. 
