112 



a pencil of setae. The last 3 pairs have the ventral border of the ischium and 

 merus closely spinose, and also have some spines and spinelets on some of the 

 other joints : their dactyli are sharp and curved and have some very fine spinelets 

 along the ventral border. 



The abdominal appendages are all biramous, and have singularly long 

 protopodites, the postero-external edge of which is beset with bristle-like 

 spinules : all the rami, except the inner ramus of the 1st pair, are long and 

 narrow: all the endopodites behind those of the 1st pair have a short internal 

 appendix, and in those of the 2nd pair in the male there are two of these. 



The exopodite of the tail-fan is imperfectly divided into two segments by 

 an incomplete transverse suture. 



The branchiae are 5 in number on either side, being pleurobranchiae attached 

 to somites X to XIV. In addition, 5 microscopic papillae are found— the vestiges 

 of lost arthrobranchiae— on somites IX-XIII. Epipodites are present on the 

 1st and 2nd maxillipeds; but on the coxae of the external maxillipecls and 1st 

 thoracic legs there are small tubercles which may be the remains of lost epipo- 

 dites. 



The efferent branchial channel is remarkably well defined by a incurved 

 process of the inflected postero-inferior angle of the carapace, the process 

 firmly catching the undermined posterior border of the last thoracic sternum. 



Key to the (Indian) species of Psalidopus. 



I. The thoracic and abdominal sterna unarmed ... ... ... p. Huxleyi. 



II. The last three thoracic and all the abdominal sterna with a needle- 

 like median spine ... ... ... ... ... P. spiniventris. 



65. JPsalidojniS Huxleyi, Wood-Mason. 



Psalidopus Huxleyi, Wood-Mason, Ann. Mag. Nat. Hist., April 1892, p. 273, pi. xiv. figs. 1, 2, 7. 

 Illustrations of the Zoology of the Investigator, Crustacea, Plate LI. Figs. 5, 5a-b. 



Rostrum nearly twice as long as the rest of the carapace, with 4 rows of 

 spines, dorsal, ventral and 2 lateral ; the dorsal row is continued to the posterior 

 border of the carapace as a spiny carina, and the lateral rows are also continued 

 to the posterior border of the carapace as sinuous spiny ridges. Besides these 

 spiny carinae, and besides many other spines, the ridges that define the branchial 

 regions above and below, and the ridge that defines the branchial canal superiorly, 

 are spiny. 



Abdomen with a median spiny carina extending to the posterior border of 

 the Gth tergum, trif urcate on the 5th tergum : with an irregular row of spines 

 on either side at the level of the junction of pleura and terga, and with other 

 spines between these rows. Tips of the pleura spinose. Dorsal surface of telson 

 thickly hispid. 



