MONOGRAPH OF THE LEUCOSIADA. 281 
exception, is restricted to its own geographical limit. There is not, I believe, a single 
instance of one species of any genus inhabiting the Old World, and another of the same 
genus being found in the New. The numerous species of what may be considered the 
typical form of the family, Leucosia, are without exception inhabitants of the Eastern seas, 
ranging from the south of Australia by the Indian Ocean, the Philippines, New Guinea, 
Borneo, the coasts of China and J apan; but strictly circumscribed to these limits, The 
genera Myra, Philyra, Myrodes, Platebalia, Txa, Iphis, Iphiculus, and Arcania are also 
confined to the same seas. Of Oreophorus one species is found in the Red Sea, and the 
other has been taken in the Straits of Sunda. balia is, as far as we are at present 
informed, confined to the tract including the coasts of Great Britain, “ La Manche,” and 
the Mediterranean; and so much is it especially a British genus, that Professor Milne- 
. Edwards, when he published his great work, had never seen a specimen of either of the 
x 
three generally known species, excepting those in the British Museum, all of which were 
natives of this country; nor does he mention a specimen of either of them as then exist- 
ing in the Paris Museum. Jia is exclusively Mediterranean. The numerous species of 
Persephona, and the new genera Leucosilia and Lithadia, are strictly American, and are 
principally found on the Eastern coasts and the Galapagos Islands. 
The majority of the species in this family are found at no great depth. 
I know of scarcely any family of Orustacea, our knowledge of the species of which has 
so much increased of late years as this. When the great text-book of the class, the 
admirable work of Milne-Edwards, appeared, there were only known to him twenty certain 
Species arranged in eleven genera. The great work of De Haan on the Crustacea of Japan 
added several others, and the list has been increased by Messrs. Adams and White in 
their description of the Crustacea from the voyage of the Samarang. The collections 
made by Mr. Cuming in the Philippine Islands and by other voyagers, have placed within 
my reach numerous others, some of which are in my own collection, but the greater number 
are in the British Museum; and I have to express my thanks to Mr. Adam White for the 
exercise of his well-known courtesy and attention in assisting my access to the treasures 
of that fine collection. In the present Monograph I have been enabled to add no less 
than thirty-six new species, thus more than doubling the number prey sanaly known ; the 
whole number now known and included in the present Monograph being sixty-five, con- 
stituting eighteen genera. 
' Genus LEUCOSIA. 
Cuar. GxN.— Testa ovato-orbicularis, subglobosa, levis, polita ; fronte subproducto, ——— ad 
tegente. Orbita fissuris tribus. Fosse anéennarie oblique, apertae tæ. ana tes Eres er 
riore lateribus parallelis, recto vel subcurvo, apice ser caule nn ; n a iili 
antici crassiores, longitudine mediocres; brachiis ad se aes Le sensim vaad Abdomen 
subinflectis; pedum paria quatuor posteriora, m T g ge ii xceptis, in aliis tertio cum 
Manis in nonnullis speciebus segmentis omnibus, PF ” N à 
quarto, et quinto cum sexto—Fœminz a tertio ad sextum coalitis. i 
The genus Leucosia must be considered as the type of the family; nieder 
perhaps generally, the case with a typical genus, it includes a much larger number of 
