LONG NAMES FOE SHORT LAEViE 221 



in the Euphausice, while on the contrary it is veiy frequent 

 among the Penseidse.' 



Family 2. — Sergestidce. 



The branchial system is impoverished or lost, the 

 epipodal plates and podobranchial plumes, when present, 

 being restricted to rudimentary structures on the second 

 maxiUipeds. The first pair of trunk-legs, and some- 

 times the second, are simple, the chelas of the third are 

 minute, the fourth and fifth pairs are feeble, rudimentary, 

 or absent, 



The genera assigned to the family are Sergestes, Milne- 

 Edwards, 1830 ; Acetes, Milne-Edwards, 1830 ; Petalidium, 

 Sp. Bate, 1881 ; Sciandris, Sp. Bate, 1881 ; and Lucifer, 

 Vaughan Thompson, 1829, a pre-occupied name altered 

 to Leucifer by Milne-Edwards in 1837. A very few re- 

 marks must suflBce on the discrimination of these genera. 

 In Sergestes the last two pairs of trunk-legs are rudi- 

 mentary, in Acetes the last but one is reduced and the last 

 is wanting, in Leucifer both pairs are absent. In Sergestes 

 the arthrobranchiffi are wanting, in Petalidium they are 

 found on the second and third maxiUipeds and the first 

 three pairs of trunk-legs. In Sergestes, Professor Smith 

 remarks, the branchise are compound phyllobranchige, 

 while those of Penwus in the preceding family are com- 

 pound triohobranchiae. 



The larval ioTvas, oi Sergestes have been partitioned into 

 genera and species. The youngest form known is desig- 

 nated Elaphocaris by Dohrn (see Plate IX.) ; another, and 

 presumably later form, is called Platysdcus by Bate ; this is 

 followed by Acanthosoma, Claus, and that by Mastigopus 

 of the same author. The species known as adults are 

 very numerous, of very various sizes, from many differing 

 localities, Sergestes atlanticus, Milne-Edwards, being found 

 both in the Mediterranean and in the Atlantic from 

 Greenland to the tropics. The account of the genus occu- 

 pies eighty-eight quarto pages and seventeen plates of 

 Spence Bate's ' Eeport on the Ghallenger Macrura.' It 



