336 DISCOVERY REPORTS 



an arthrobranch ; maxillipede 3 to leg 4 with epipod and two gills, decreasing in size 



backwards. 



Four pairs of minute pleopods. Uropods large, exopod without spine. 



This larva agrees in stage I so closely with that of Natishonia crangonoides as described 

 by Thompson that I had no hesitation in supposing it to belong to that genus. The 

 only difference between them lies in the absence of pleural spines from the abdomen 

 and the presence of papilliform processes on somite 5 in the Samoan form. The later 

 stage from the Barrier Reef, which seems to belong to the same species, differs in the 



a. Side view. 

 d. Maxillule. 



Fig. 37. Naiishonia} B.R.I. Stage IV? 

 b. Telson. 

 e. Maxilla. 



c. Right mandible. 



same way from A^. crangonoides, but also lacks the exopod shown by Thompson on 

 leg 4, and has the head region distinctly more elongated. There are also small differences 

 in the telson, though the general form of it is the same. The presence of a rudimentary 

 arthrobranch on maxillipede i is a point of considerable importance, since it is present 

 in Jaxea and Naushonia but not, so far as is known, in other Thalassinidea. The larva 

 may be said to resemble Naushonia more closely than it does Jaxea, and may well 

 belong to that genus; but I am inclined to think that the differences are more than 

 specific, and that it actually belongs to a distinct genus. 



Thompson (1903) pointed out the close resemblance between both larva and adult 

 of Naushonia and Jaxea. Previously there had been some doubt as to its position and. 



