LR. Lydekker—Catalogue of Fossil Reptilia, ete. 451 
action must at least be continued somewhere back in early geological 
time, and would render any astronomer or physicist most impatient 
in hurrying geologists up for time. Lastly, where have all the 
resulting materials gone? for they would be sufficient to entirely 
change the south slopes of the mountain. Had my critic studied 
the field geology of that region near the coast, he might observe the 
pumices of Phase VI. covered only by a few metres of alluvial 
breccia. 
Lastly, if Prof. Franco’s explanation was feasible, it should be 
applicable to all the voleanoes in its neighbourhood. Now, Rocca- 
monfina, which so strikingly resembles Vesuvius in size, shape, and 
many of its rocks, has the lower lip of its crater of explosion directed 
to the opposite points of the compass, to that of Monte Somma, but 
no one would dare assert the prevailing winds to differ at Rocca- 
monfina. 
Conclusions.—That the picture discussed by the author is a very 
fair representation of Somma truncated by an eccentric crater pro- 
duced by the explosive eruptions of Phase VI. 
That ancient writers’ accounts correspond fairly well with this 
figure, and the result of geological investigations. 
That the Plinian eruption took place together with its successors 
around the same axis, as the explosive eruptions of Phase VI. 
I would remark that this is a general statement; it is highly 
probable that not one of the great eruptions were from exactly the 
same geometrical axis; but by saying the same amis, I understand 
approximatively the same for practical considerations. In fact, it is 
very doubtful if the axis is exactly fixed during the whole period of 
any one single eruption. 
In fine, I am deeply indebted to my friend Prof. Franco for so 
patiently discussing the historical part of the subject, and for giving 
us such a rich classical and literary treat, and really hope he will 
take up some other similar knotty questions bearing on such an 
interesting geological region. 
TV.—Brirish Museum Caranocuk or Fossit Repritia, AND PAPERS 
ON THE HENALIOSAURIANS. 
By R. Lyprexxer, B.A., F.G.S., ete. 
N writing Part I. of the British Museum Catalogue of Fossil 
Reptilia, in which a large number of forms are known solely 
by disjecta membra, I was fully prepared to find that many of my 
determinations, which are frequently provisional, would subsequently 
need correction. It is, moreover, highly probable that there are 
really more species represented in the collection than I have indicated, 
as in some cases, in my desire to avoid the introduction of new 
specific or generic names which could not be fully substantiated, I 
have provisionally included under generic or specific headings 
specimens which may prove to indicate distinct forms. I have 
lately had the advantage of going over a considerable part of the 
Dinosaurian collection with Prof. Marsh, who has pointed out to me 
several erroneous determinations, the most important of which I am 
