toU- CoLGAN. — Opisthohmnck Fauna of Co. Dublin. 191 
already mentioned, the Mediterranean L. Eisigii of Trin- 
chese (Journ. Marine Biol. Assoc., vol. i., p. 18-^-9, 1889), 
Another authority, W. I. Beaumont, admits two species, 
one L. Genei, including all the large, the other, L. marmoratus 
all the small forms (Beaumont, 1900). Again, Sir C. Eliot, 
in his Notes on some British Nudibranchs [Journ. Marine 
Biol. Association, vh., 1906), accepts provisionally three 
species, one, L. Genei for the large forms, two others, L. 
maruwratus and L. flavidus, for the small. The present 
writer in the belief that the extension of the pallial margin 
into a caudal, fin-like process in L. portlandicaus and L. 
Eisigii, might be a sufficient specific character, united 
these into one species under the name L. portlandicus, 
while referring all the other forms, large and small, to a 
second species for which he retained the name marmora- 
tus as having priority over L. Genei [Colgan, 'o8b). Finally, 
G. P. Farran, influenced chiefly by marked numerical 
differences which he has detected in the divisions of the 
radulae, allocates the large Irish specimens to two species, 
one L. portlandicus for the Eastern or Irish Sea form, the 
other, L. Genei, for the dark coloured Atlantic or west 
Irish form. Sir C. Eliot (Part viii. Aid. & Hancock's 
Monograph, Ray Soc, 1910) failing to find the differences 
pointed out by Farran, does not admit their constancy 
and continues to regard L. Genei and L. portlandicus as one 
species. 
As for the eleven small and presumably immature speci- 
mens taken at Skerries in 1911-12, they fall under three 
of the described species which are here, provisionally at 
least, fused into one. Two specimens, one 4 mm,, the 
other 12 mm. in length, with brown marblings on a whitish 
ground, agreed closely in general aspect with L. marmora- 
tus ; a third, 7 mm. long, in colour light yellow with 
brown llecks on the papillae, agreed perfectly in lorm and 
colour with L. flavidus ; seven others, the small specimens 
taken in July, 1912, ranging from i • 5 to 6 mm. in length, and 
translucent white flushed with pink, were clearly juvenile 
states of the large Irish Sea form referred by Mr. Farran to 
L. portlandicus, a form with which the large Bullock specimen 
of 1906 agreed perfectly. The last or eleventh of the small 
