DK. BOAS ON THE SQUILLHXSS 279 



CHAPTER XIX 



SUB-ORDER IV. STOMATOPODA 



THE carapace is feebly developed, leaving uncovered at 

 least the last three segments of the trunk ; the pleon is 

 powerful, and, like the carapace, usually depressed, not 

 laterally compressed. The eyes are stalked. The second 

 antennas have a scale. The mandibles have a small or 

 rudimentary ' palp.' The three pairs of maxillipeds and 

 the two following pairs of appendages are variously modified 

 as six-jointed prehensile limbs, with epipods, but without 

 exopods ; the second maxillipeds being predominant in 

 size and importance. The three following pairs of legs are 

 feebly developed, with exopods, but without epipods. The 

 first five pairs of pleopods generally carry each a pair of large 

 ramified branchias arising from the outer branch. There 

 is a special apparatus on the inner branch of the first 

 pleopods in the male. The caudal fan is powerful. The 

 heart is elongate, with several pairs of lateral venous fis- 

 sures. The ovaries and testes lie chiefly in the pleon, and 

 have their two halves united by a median piece. There are 

 no spermatophores. The spermatozoa are simple, rounded 

 cells. The young are hatched not as Nauplii, but in a more 

 advanced stage. The carapace of the young is largely 

 expanded. 



The above definition is chiefly taken from that given 

 by Dr. J. E. V. Boas for the ' Order Squillacea,' in his 

 highly esteemed ' Studies on the Relationships of the Mala- 

 costraca.' It is in this sub-order that the typical number 

 of twenty-one segments has been distinguished in a 

 single animal. Usually the first antennas have three flagella, 

 one of the two principal ones sending off a branch from 



