THE POINT EXPLAINED 123 
CHAPTER IX 
TRIBE IV.—OXYSTOMATA 
THE carapace is convex or depressed, with the antero- 
lateral margins arcuate or orbiculate ; or even subglobose ; 
or more or less oblong, with subparallel or slightly con- 
vergent margins (Dorippide). ‘The epistome is very much 
reduced or rudimentary. ‘The buccal frame is more or 
less triangular, nearly always produced and narrowed 
forwards with the margins anteriorly convergent. ‘The 
afferent channels to the branchiz open either behind the 
pterygostomian regions and in front of the chelipeds, or, 
more rarely, at the antero-lateral angles of the palate 
(Leucosiidee). The efferent channels open at the middle 
of the endostome which is produced forwards. ‘There are 
six to nine pairs of branchie. The first antenne fold 
longitudinally or obliquely. The third maxillipeds have 
the fifth joit articulated at the inner or the outer front 
angle or at the apex of the fourth, beneath which it is 
often concealed. The verges of the male are exserted 
either from the surface of the sternal plastron or more 
usually from the bases of the fifth pair of legs, which are 
either adapted for walking or for swimming, or are feeble 
and raised upon the dorsal surface of the carapace. 
It is the narrowing anteriorly of the buccal frame or 
mouth-cavity ’ that gives the name of ‘sharp-mouths’ to 
this tribe, which is divided into four families, the Calap- 
pide, Matutidz, Leucosiidz, and Dorippidee. 
Family 1.—Calappide. 
The afferent channels to the branchiz open bebind 
the pterygostomian regions and in front of the chelipeds. 
