2 
not be left: the author of a new generic name should state, when he creates 
it, not only which species, but exactly and without ambiguity which speci- 
men of that species is to be taken as genolectotype — which specimen is an 
important proviso, for with the best of skill and intention an author may 
be mistaken in his identification; therefore, if he leave the question open 
between various specimens belonging, as he thinks, to one species, he is 
leaving, possibly, a legacy of trouble. If he leave it open between many 
species he is risking disaster. 
The genotype of Macrocephalites is Macrocephalites macrocephalus 
Zittel 1 (not Ammonites macrocephalus Schlotheim) from “Callovian, 
Ehningen (Wurttemberg)” (Fig. 655, p. 470). He gives a woodcut repre- 
senting the side-view of the specimen, but does not say whether it is natural 
size or reduced. This omission is serious, for a large species with coarse, 
somewhat distant ribs apes, when reduced, the form of a small species 
with fine ribs: this is misleading. But there is a more serious omission — 
no suture-line is figured. The information is given that the suture-line is 
“tief zerschlitzt” — deeply divided. There are certainly two species like 
ZitteFs figure, supposing it to be of natural size: one has quite a simple 
suture-line, the other has a very elaborate one. Like as it is, therefore, 
to ZitteFs figure the first one may, perhaps, be ruled out, but it is not 
certain that the second one can be accepted. Deeply divided is not an 
exact term : it might be applied to a suture-line less elaborate than that of 
the second one. The possibility that there may be a third like species — 
one intermediate in regard to suture-line — is not to be overlooked: the 
suture-line of such third hypothetical form might be called deeply divided 
without being so remarkably elaborate as that of the form No. 2. But, 
further, Zittel has not given the necessary evidence that he actually 
described the suture-line from the specimen that he figured. This may 
not have shown a suture-line: the observation as to suture-line may have 
been made from another, apparently quite similar, example. From the 
remarks made above, it can be seen how unsafe and misleading this may 
possibly be. Therefore, at the very outset it is obvious that this investi- 
gation is not as simple as it should be considering the work done. In order 
to lay a really sure foundation it is necessary to see the actual specimen 
that was portrayed in ZitteFs woodcut. But here may be trouble; the 
woodcut may not be an original one, it may be merely a copy of some 
figure, so much reduced as to be recognizable with difficulty. 
The interpretations that have been given of ZitteFs figure are notable. 
Parona and Bonarelli (p. 118) cite ZitteFs figure in their synonymy of 
Macrocephalites canizzaroi (Gemmellaro), and then say that this species 
“est la forme la plus comprim^e du groupe des [ Macrocephali ] rectecostati” 
But ZitteFs figure does not show truly straight ribs: they are mainly 
arcuate, in places somewhat S-shaped, on the lateral area. I have not 
been able to see the original figure of Stephanoceras canizzaroi Gemmellaro 
(1, Pl. IX, figs. 9-11), as the work is not in the Library of the Geological 
Society of London; but Dr. L. F. Spath kindly informs me that “Gem- 
mellaro’s canizzaroi is a slightly distorted specimen of probably the same 
species as his later macrocephalus ” (2, PI. iv, fig. 1) : this is a flexiradiate 
form. 
* See alto page 8. 
