42 
Proceedings of the Royal Irish Academ/ij. 
terranean shells, amongst which are several specimens of C. tyrrhem, 
all of which are unmistakably similar to our form, and can be readily- 
distinguished from ordinary specimens of C. echinophora. The follow- 
ing are the localities of the specimens of C. tyrrhena in the Science 
and Art Museum, Dublin : — Three specimens from Palermo, in. 
long by 1^6- in. diameter ; 2\% in. by l-^ in. ; in. by 1^ in., respec- 
tively; two specimens of ''var. atlantica^'' from off Arcachon, 3^ in. 
long by l-rf in. in diameter — one, at all events, being from a depth 
of 802 fathoms (" brasses"). Our specimens agree perfectly with the 
above-mentioned examples of var. atlanticaP This variety is a much 
larger and finer shell than the Mediterranean form. 
The overlapping of species characteristic of the Lusitanian and Boreal 
regions oJffi the south-west of Ireland has been noted before. Our two 
expeditions have advanced additional evidence of this fact. For ex- 
ample, of southern forms we found Gephyra dohrnii and Ophiothrix 
lutheni, in addition to the well-known Strongylocentrotus lividus ; while 
Solothuria tremula^ Brisinga endecacnemos, Pontaster tenuispinus, and 
possibly Actinauge richardi represented the southward migration of 
northern species. This interdigitation of faunae was, however, most 
markedly demonstrated, when in the same trawl a couple of brilliant 
Holothuria tremula were associated with two very fine specimens of 
Cassidaria tyrrhena, one of the most characteristic of the Mediter- 
ranean shells. I at once recalled the somewhat similar experience 
narrated by the Eev. Canon Norman, in his "l^otes on the French 
Exploration of ' Le Travailleur' in the Bay of Biscay" (Ann. and Mag. 
of jN'at. Hist. (5), vi., 1880, pp. 430-436) : he states : — A curious in- 
stance occurred of the meeting in the Bay of Biscay of species hitherto 
supposed to be confined to Scandinavia, with others regarded as emi- 
nently Mediterranean. The trawl had been down in 360 metres, and 
when taken up, out of it rolled one or two hundred large Holothurians, 
each about a foot long. It was at once evident that they belonged to 
two species ; and further examination proved about two-thirds of them 
to be the rosy-coloured Holothuria tremula of I^"orway ; the remainder, 
known at a glance by their light-brown colour and flattened side, were 
Stichopus regalis of the Mediterranean. They had apparently met on 
this neutral ground, and were living together on the most amicable 
terms." 
It was quite late by the time the trawl was up, and we then 
steamed for Berehaven, where we arrived the next morning at 3 a.m., 
running before a high sea. 
A little dredging was done in Berehaven on our old ground, but 
