rifTKODirCTION. 
vm 
9. Ornati {=^Discites &c.).— Containing three species, viz. Nau- 
tilus discors, M‘Coy, N. Leveilleanus, de Kon., N. onia- 
tissimiis, de Kon. 
In this arrangement the form of the shell in nearly all the divi- 
sions is taken as the basis of the classification, which thus approaches 
nearer to a natural one than d’Orbigny’s. Exception, however, 
must he taken to Group 9, Ornati, which is not of equal value with 
the other groups, and includes species whose shell-characters indicate 
very clearly their alliance with Group 5, Bisciformes, (See infra, 
pp. 86-96.) 
It may he mentioned that a careful diagnosis of the characters of 
all the species comprised in the above groups is given in de Kon- 
inck’s table, under the following headings, viz. : General Form ; 
Surface, Spire, Transverse Section ; Umbilicus, Sutures ; Siphuncle. 
The following groups are adopted by Mojsisovics^ in his work on 
the Alpine Trias : — 
The following Families ^ of the Kautiloidea, and many of the 
genera comprised in the former, were proposed by Professor Hyatt 
in his ‘ Genera of Fossil Cephalopods ’ (1883). I have here tran- 
scribed only those Families which include genera treated of in the 
present volume, such genera being distinguished by an asterisk. 
Beginning with the Hercoeeratidae (‘ Genera Foss. Ceph.’ p. 282), 
all the families are given in the same order as in Hyatt’s memoir, 
except that I have added at the beginning his provisional Family, 
Tainoceratidce, placed by him under the heading “ Incertse Sedis ” 
(‘ Genera Foss. Ceph.’ p. 267). This Family is included by Hyatt 
(with a reservation as to some of the genera) in his division Holo- 
choanoida and immediately succeeds the EndoceratidcB in his 
^ Die Cephalopoden der Mediterranen Triasprovinz (Abhandl. d. k,-k. geol. 
Keiehsanst. Band x.), 1882, pp. 265-290. 
^ See Coelonantilus, mfra, p. 105. 
^ Excepting, of course, the Nautilida. 
* See Part I., Introduction, p. v. 
Family KAUTILIDH]. 
Pleuronautilus (Mojs.). 
