BEAUTIFUL COLOURING 127 



Sfimpson, and Adceomorpha, Miers, are distinguished from 

 Matuta by having the terminal joints of the legs adapted, 

 not for swimming, but for walking. Osachila and Adceo- 

 morpha are, according to the author of the latter genus, 

 perhaps identical. 



Family 3. — Leucosiidce. 



The afferent channels to the branchi^ open at the 

 antero-lateral angles of the endostome and not behind the 

 pterygostomian regions. The third maxillipeds have the 

 three terminal joints wholly concealed by the triangular 

 fourth joint. The verges of the male are exserted from 

 the sternal plastron. 



In this family twenty-nine genera are accepted by 

 Miers in 1886. One of them is included in the fauna of 

 Great Britain. 



Leucosia, Fabricius, 1798, contains numerous species, 

 which occur in the littoral and shallow waters of the Indo- 

 Pacific region. They are often remarkable for the beauty 

 of their colouring, testimony to which is borne in the 

 names of the species, Leucosia splendida, Haswell, and 

 Leucosia pulcherrima, Miers. They have the frontal re- 

 gion of the carapace narrowed and produced anteriorly, 

 and in front of and above the bases of the chelipeds there 

 is a pit defined by a series of granules. This, which is 

 continued as a shallow excavation beneath the postero- 

 lateral margins of the carapace, has received the name of 

 the thoracic sinus. The walking-legs are small, succes- 

 sively shorter from the front to the rear. The pleon of 

 the male in some species has all the segments united ex- 

 cept the first and last, in others the third coalesced with 

 the fourth, and the fifth with the sixth. A figure of 

 Leucosia australiensis, Miers, is given on Plate II. The 

 type species, scahriuscula, Fabricius, has been transferred 

 to the next genus. 



Pliilyra^ Leach, 1817, is a genus nearly allied to Jjeu- 

 cosia, wdth a similar range, and also containing several 

 species. But, among other distinctions, the ' front ' is 



