MONOGRAPH OF THE LEUCOSLUXE. 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 Japan ; but strictly circumscribed to these limits. The 

 genera Myra, Philyra, Myrodes, Platebalia, Ixa, 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. JEbalia 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 

 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. Ilia 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 Crustacea, 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 previously known ; the 

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

 stituting eighteen genera. 



Genus Letjcosia. 



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

 tegente. Orbita fissuris tribus. Fossae antennarioz obliquae, apertae. Pedipalpi 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 

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

 Maris in nonnullis speciebus segmentis omnibus, primo et ultimo exceptis, in aliis tertio cum 

 quarto, et quinto cum sexto — Fcemin^e 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 



