THE MEDITERRANEAN NATURALIST 
253 
of Caserto they die off gradual ly, and the plain at 
their foot is but slightly above the sea level: From 
Cape Posillipo as far as the Vomero, above the 
Grotta di Pozzuoli, the hill is saddleshaped, with 
a long, narrow, ridge at the summit, and sloping 
down at a considerable angle on either side to the 
base. At the distance of half a mile from the 
mainland beyond Cape Posillipo is the little islet 
of Nisita, ISO m. high, and which is simply a small 
volcanic cone, with a crater broken down on the 
side looking towards the entrance of the bay, 
the rock consisting of volcanic tufa. 
It has always been a question to me whence 
this prodigious mass of tufa overlooking the Bay 
of Naples was ejected. Certainly not from Vesu- 
vius or Monte Somma, far less from certain other 
volcanoes, such as the Solfatara, the Astruni, or 
Agnana, which have not the least topographical 
connection with the hills of which I am speaking, 
and no denudation has taken place to authorize 
such a supposition; most improbably also from 
Gisita, which, besides its insignificant proportions 
occupies too eccentric a position. For my part 
some day to be able to communicate further in- 
formation regarding it. I am led to conclude that 
the central crater of this volcano must have been 
situated within a mile of the present coast line 
in a spot now occupied by deep rvater, the cone 
having subsided since the quaternary period. 
Should my conjecture be found admissible we 
might apply the name of Mergellina volcano to 
this track ''tic ejection, and we might then be 
authorized to regard the tufa hills of Naples, as 
Sasillino as having had their oringin thence. 
Both the trachyte and the yellow tufa are rocks 
common to all the volcanoes of the Phlegnean 
Fields and the neighbouring islands while leucitic 
rocks characterize Monte Somma and augite and 
Vesuvian leucite rocks. 
While speaking of the neighbourhood of Naples 
I may just give the results of a few very careful 
observations I made this spring of the temperature 
of several thermal springs and fumaroles, and 
compare them with former studies. 
Casamiceiola, Island of Ischia. — Acqua del Gur- 
r iitelto ; February I860, 84°. c. (Jervis); 10th May 
1892, 84°. c. (Jervis). 
Lacco Ameno, Island of Ischia . — Acquadella Rita 
1833, 70°. c. (Dellivaz); 1835,61°. c. (Guarini); 11th 
May 1892, 66". c. (Jervis). 
Barano d’Ischia .—Fumarola. di. Saint' Angela , 
on the beach; February 1869, 100°, c., (Jervis); 
lltla May 1892, 100°. c. (Jervis). 
Casamiceiola. — Stufe or Fumarole di Cast iglione 
1822, upper fumarole 56°. c. lower fumarole 66". c. 
(Del Giudiee); 11th May 1892, lower fumarole, 56°. 
c. (Jervis). 
Puzzuoli. -Fumarola della Ilocca della Solfata- 
ra ; February 1862, 93’.4 — 96’. 5 c. (Deville); June 
1SG5, 77". — 96°. c. (Deville); 1865, 96°. c. Fouque); 
July 1867, 115°. c. (Goreix;) January 1869, 92°. c. 
(Jervis); 12 May 1892, 95°. c. (Jervis). 
Naples. — Stufe di San Germano ; 1856, 64° — 93°. 
•c. (Deville); 1857 and 1882, 61° — 97°. c. (Deville); 
1857 and 1862, 61°.— 97°. c. (Deville); July 1869 
85" — 96°. c. (Deville); May 1892, 86°. c. (Jervis). 
Naples. — Acqua del lar/o ]>rosciugato di Agnana 
May 1892, 69° — 73'. c., according to place (Jervis). 
Naples. — Grotta del cane ; May 1892, 38°. c. 
(Jervis). 
G. Jervis. 
Turin, September 1892. 
On Tryonx Ragusensis, and T. Melitensis. 
Be Greg. Lyd.elc. 
In a short article contributed to II Naturalista 
Sicilian o Professor De Gregorio says of the above 
fossils. 
“ In 1883 I had several fossils sent to me for 
determination from the Geological museum of 
Modica, amongst which was an interesting portion 
of a carapace, which in a note written in 1883 
(Nucvi Fossili vert, e invert, p. 1)1 called Tryonx 
Ragusensis. I had the specimen figured but I did 
not publish its description in extenso. Mr. R. 
Lydekker in his paper on a “ New species of 
Tryonx from the Miocene of Malta ” (1) figures a 
species which at first sight seems to be analogous 
to our species. My friend Mr. Negri showed me 
a few months ago some beautiful drawings of an 
analagous species from the lower tertiary of Vicen- 
za Monteriale. I believe that all of these forms, 
as I have remarked in aforesaid notes, are to be 
grouped with the Tryonx italicus Schaue and 
Hewrici Owen.” 
(1) Quart, .Town. Geol. Soc. v. 1S5. TV. 37. 1801. 
