470 CRUSTACEA. 



In the female the posterior antennae are short and rudimentary, 

 while in the adult male they, together with their niultiarticulate 

 flagellum, may be as long as the body (as in Nebalia). The upper-lip 

 is usually small, while the deeply cleft under-lip is of considerable 

 size. The mandibles are without palps, and possess a comb of bristles 

 and a powerful masticatory process below their strongly toothed 

 extremity. The anterior maxillae consist of two toothed blades and 

 a cylindrical, flagellate appendage directed backwards. The unpalped 

 maxilla of the second pair is composed of several pairs of masticatory 

 plates lying one above another. The two following pairs of 

 appendages may be distinguished as maxillipeds. The anterior, 

 which corresponds to the palped under-lip of the Isopoda, is five- 

 jointed and may be recognised by the process of the basal joint ; the 

 posterior, which is also usually five-jointed, is of considerable length 

 and the basal joint is cylindrical and elongated. They also bear the 

 large pinnate gill and a peculiar plate. Of the remaining six pairs 

 of thoracic appendages, the two anterior are always formed like the 

 feet of the Schizopoda ; they consist of a six-jointed leg, the basal 

 joint being strongly developed and lamellar, and of a multiarticulate 

 accessory ramus (exopodite) beset with long swimming set*. The 

 four last pairs of appendages are also six-jointed, but are shorter ; 

 they bear in many cases, with the invariable exception of the last 

 pair, a larger or smaller swimming appendage as exopodite. The 

 very narrow and elongated abdomen is, in the female, entirely without 

 swimming feet, but bears on the large sixth segment at the sides of 

 the caudal plate long-stalked biramous caudal styles ; while in the 

 male two, three or five pairs of swimming feet may in addition be 

 present on the preceding segments. 



Fam. Diastylidae. JJluxti/Jin lluthltti Kr., North Sea. I). Edicdrdxii Kr. 

 Leucon naxicns Kr. , Norway. 



(2) Sub-order: Stomatopoda. :;: 



Elongated Thoracostraca with short cephalo-thoracic shield tvhich 

 does not cover the thoracic segments. There are, jive, pair oj ma.cilh- 

 pedsand three pair of biramous thoracic feet. The sioimming feet on 

 the strongly developed abdomen bear branchial tufts. 



* Besides Dana, M. Edwards and others, compare 0. Fr. Miiller. " Bruch- 

 stiick fius der Entwickelungsgeschichie der |lanlfusser," I. and II., Arcliir fiir 

 Natiirgcxcli., Tom XXVIII..' 1862, and Tom XXIX., 18(53. C. Clans, " Die 

 Metamorphose der Squilliden," Alluuull. der Gottinyrr ^ncirtat, 1872. C. 

 Grobbcn, " Die Geschlechtsorg-ane von Squilla mantis," SitzunyxJirr. dt-r /.'. 

 Aliad. der Wixsen&sft., Wien, 187(i. 



