136 A. Alcock — Carcinological Fauna of India. [No. 2, 



The afferent branchial openings are found either in the usual place 

 in front of the bases of the chelipeds, or at the sides of the endostome. 



Branchiae from six to nine on either side. 



The antennules fold either longitudinally or obliquely, very rarely 

 transversely. 



In the male the genital ducts protrude either through the bases of 

 the fifth pair of legs or through the fifth thoracic sternum close by. 



The Oxystoma may be divided into four families as follows : — 



Family I. Galappidse. Carapace of the ordinary brachyurou3 

 shape. The afferent branchial openings are found in front of the bases 

 of the chelipeds. The antennae are small. The legs are normal in 

 position. The vasa deferentia perforate the bases of the fifth pair of 

 legs. The branchiae are nine in number on either side. The external 

 maxillipeds either completely cover the buccal cavern and have their 

 palp hidden in repose (Matutinse), or do not close the buccal cavern and 

 have their palp always exposed {Galappinse) . 



Family II. Leucosiidse. The carapace is of the ordinary brachv- 

 urous shape. The afferent branchial channels are found on either side 

 of the endostome. The vasa deferentia perforate the sternum near the 

 bases of the fifth pair of legs. The legs are normal in position. The 

 antenna? are small, sometimes obsolete. The external maxillipeds com- 

 pletely close the buccal cavern and have the palp completely hidden in 

 repose. The branchiae are less than nine (six in many forms) in number 

 on either side. 



Family III. Dorippidse. The carapace is short, so that the first 

 two or three abdominal terga, instead of being tucked up beneath it, 

 are Completely exposed in the dorsal plane of the body. The last two 

 pairs of legs are much reduced in size and have a peculiar position in 

 the dorsal plane of the body. The antennae are large. The antennules 

 are usually too large to fold into their fossettes. The vasa deferentia 

 emerge through the sternum near the bases of the fifth pair of legs. 

 The afferent branchial openings are found either in front of the bases 

 of the chelipeds or not. The external maxillioeds either do cover the 

 buccal frame (Tyrnolinas), or do not (Dorippinse) . The branchiae are 

 less than nine in number on either side. 



Family IV. Baninidse. Carapace remarkably elongate, but not 

 covering the abdominal terga, the first 4 or 5 of which lie exposed in the 

 dorsal plane of the body. The last pair of legs also is raised in the 

 dorsal plane of the body. The antennae are large. The antennules also 

 are large, and do not fold into fossettes. The vasa deferentia protrude 

 through the bases of the fifth pair of legs: the oviducts pierce the bases 



