XVI 
IXTEODTJCTIOX. 
laterally compressed whorls and a more or less truncated periphery, 
and two of them {K polijgonalis and N. glaber) agree in having 
markedly sinuous sutures, differing in this point from the other 
two species, and making a very perceptible approach to Hercoglossa. 
Similarly, Nautilus suhtriincatus, Morris and Lycett, N. clausus, 
d’Orbigny, and N. lineolatus, Foord and G. C. Crick, are regarded 
as allied species \ because all of them have remarkably thick, sub- 
quadrate whorls, similar sutures, and a smooth test. 
Passing on to the Cretaceous rocks, a group of species is met 
with, characterized by more or less coarse transverse costae. 
Nautilus elegans, J. Sowerhy, might be taken as the type of this 
group, which is made up of the following related species : N. jgseu- 
doelegans, d’Orbigny, N. elegantoides, d’Orbiguy, and N. Atlas, 
Whiteaves This group, which probably includes other species, 
is evidently equivalent to Hyatt’s genus Cgmatoceras, of which 
N. pseudoelegam was chosen for the type ^ 
In the Tertiary I have no groups of species to suggest; two 
species which differ from the rest in the sinuous characters of their 
sutures, being placed on that account in the subgenus Ilercoglossa. 
These are Nautilus (Hercoglossa) Cassinianus, Foord and G. C. 
Crick, and N. (H.) ^gyptiacus, Foord. 
An eminent palaeontologist has taken occasion, in a recent work ■*, 
to utter a protest against the excessive multiplication of specific and 
varietal names. While admitting the great desirablity of simplify- 
ing scientific nomenclature by reducing, as much as possible, the 
number of species, we must be very careful not to err in the opposite 
direction. It is only by taking cognizance of the most minute 
variations of individuals that it becomes possible to trace out the 
development of a group of fossils in geological time. It should be 
recollected, moreover, that the palaeontological species rests upon a 
very different basis from that of the zoological one. The former, 
owing to the entire destruction of the soft parts of the animal. 
’ See infra, pp. 222-228. 
^ See Foord and G. C. Crick, Geol. Mag. dec. iii. vol. vii. 1890, p. 542. 
^ Proceed. Boston Soc. Nat. Hist. vol. xxii. 1883, p. 301. 
^ A. Gaudry, ‘ Les Enchainements du monde animal dans les temps geo lo - 
giques.’ Fossiles Secondaires. 1890. 
