MONOGRAPH OF THE LEUCOSIADiE. 281 



exception, is resti'icted to its own 2:eogra])]iical limit. There is not, I believe, a single 

 instance of one species of any genus inlialnting 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 Japan ; but strictly cu-cumscribed to these Umits. TIu^ 

 genera Ilyra, Ph'tlyra, 3£yrodes, i^lmiobaik *, Ixa, Iphis, Iphlculus, and Arcania are also PA7tr 

 confined to the same seas. Of Oreophorits one species is found in the Red Sea, and the 

 other has been taken in the Straits of Sunda. Ebalia is, as far as w^e 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 Mihie- 

 Edwards, when he pul)lished his great work, had never seen a specimen of either of the 

 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 cither of them as then exist- 

 ing in the Paris Museum. Ilia is exclusively Mediterranean. The numerous species of 

 Perscphona, 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 Crustacea, oiu" knowledge of the species of wliich has 

 so much increased of late years as this. "Wlien the great text-lwok of the class, the 

 admii'able work of Milne-Edwards, appeared, there were only known to liim 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 

 theii- 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 ow^l collection, but the greater numl^er 

 are in the British Musciun ; and I have to express my thanks to Mr. Adam "V\Tiite for the 

 exercise of his well-knoAvn courtesy and attention in assisting my access to the treasm'es 

 of that iine collection. In the present Monograph I have been enabled to add no less 

 than thirty-six new species, thus more than doubling the number previously known ; the 

 whole number now known and included in the present Monograph being sixty-five, con- 

 stituting eighteen genera. 



Genus Leucosia. 



Char. Gen. — Testa ovato-orbicularis, subglobosa, laevis, polita; fronte subproducto, fossulas antennarias 

 tegente. Orhita fissuris tribus. Fossce antennarite obliqua, apertae. Pedipulpi externi caule exte- 

 riore lateribus parallelis, recto vel subcurvo, apice obtuso ; caule interiore acute triangulari. Pedes 

 antici crassiores, longitudine mediocres ; brachiis ad basin et ad latera tuberculatis ; digitis tenuibus 

 subinQectis; pedum paria quatuor posteriora, a secundo ad quintum sensim breviora. Abdomen 

 Maris in nonnuUis speciebus segmentis omnibus, prima et ultimo exceptis, in aliis tertio cum 

 quarto, et quinto cum sexto — Fcemin^ a tertio ad sextum coalitis. 



The genus Leucosia must be considered as the type of the family ; and, as is often, 

 perhaps generally, the case with a typical genus, it includes a much larger number of 



