198 MR. P. S. ABRAHAM ON THE [ Mar. 6, 
merated 17 (a few of them new) from the Mediterranean ; Philippi, 
who recorded 23 from Sicily; Lovén, who found 18 (5 new) on the 
Scandinavian shores; Verany, who described 11 new species, and 
enumerated 1] others from the Gulf of Genoa, and who afterwards 
catalogued 23 from the environs of Nice. Kelaart has described 42 
from Ceylon ; Angas, 21 from New South Wales; Alder and Han- 
cock, 32 from India and Ceylon; Gould, 9 species from Eastern 
North America, and 14 from the Pacific Isles; Pease, 28 from the 
same part of the world. Recently Bergh has figured, described, or 
named about 32 species of Anthobranchiate Nudibranchiata from 
the Philippine archipelago. In addition, De Blainville, Leach, Gray, 
Fischer, Mérch, and several other naturalists have more or less 
studied the group, and have from time to time added species to the 
list. With the exception of Cuvier, Delle Chiaje, Johnston, Alder, 
Hancock, Embleton, and Bergh, few observers have examined the 
anatomy of this section of the order. 
Between the years 1845 and 1855, appeared Alder and Hancock’s 
‘Monograph of the British Nudibranchiate Mollusca.’ This is 
by far the most important work that has ever been writien on the 
naked-gilled Mollusca. In it 39 species of our native Antho- 
branchiata areineluded, and 29 of them minutely described and beauti- 
fully figured. Twenty-two were new or but recently described by 
the authors ; and, for the first time, something like a philosophical 
classification of the Nudibranchiata was proposed. Upon that 
arrangement is based, in a great measure, the plan adopted in the 
present paper. 
The Anthobranchiate naked-gilled Mollusks are found all over 
the globe, frequenting, for the most part, rocky shores between 
high- and low-water mark. Some, however, have been dredged 
from comparatively deep water, or have been found on floating sea- 
weed. They appear to be more numerous, larger, and with more 
brilliant colours in the warmer seas, especially in those of the eastern 
hemisphere. Some of them have a wonderfully wide “habitat.” 
In the British Museum there are specimens of the common European 
Doris tuberculata, which were obtained from New Zealand and from 
Vancouver Island. Lamellidoris bilamellata, also one of the 
commonest of North-European Dorididee, is found on both coasts of 
North America ; and several other instances might be given. The 
Americah forms are, as a rule, few, small, and obscure in colouring. 
The small, brightly coloured Chromodorides are all inhabitants of 
warm seas; while the Polycerides have principally been discovered 
on the colder shores. The Indian and Pacific Oceans seem to be 
the head quarters of the remarkable tongueless Doridopsidee ; but 
a few have extended so far north as the Mediterranean. 
