280 MR. BELL, HORjE CARCINOLOGIC^E ; 



pedes in eodem piano inserti ; orificia generationis masculina in sterno loeata, foeminina 

 in medio articulo tertio sterni ; abdomen arete cum sterno cohaerens, operculiforme, in 

 maritms 4- vel 5-, in fremitus 5-articulatum ; abdominis articuli primi organa vaginseformia 

 recta vel spiralia basi sejuncta in Leucosiis, vel compressa basi conjuncta in Iliis ; organa 

 excitantia articuli secundi, aut tertiam partem anteriorum sequant in Leucosiis, aut plane 

 desiderantur in Iliis et Philyris ; appendices abdominales foeminarum externa? oblongae 

 foliaceae et internse setacese sub angulo recto geniculatae." 



I will now offer a few general remarks which may illustrate the bearing of their struc- 

 ture upon their habits. This structure is evidently not fitted for any rapid or energetic 

 movements such as belong to the Grapsidce and Ocypodidce, in which these powers are 

 amply provided for by the robust form and development of the ambulatory pairs of legs ; 

 nor does it afford any means of svdmming, as in the Portunidee, or still more in Matuta ; 

 nor is it fossorial, as in Carcmus and many others ; nor suited for climbing, as in the long 

 slender-legged Leptopodiadce ; nor for self-concealment, as in the Calappadce. It appears 

 that they must depend for their safety from external injury upon the protection of stones 

 and the hollows of rocks ; for their claws have no power of defence, and the ambulatory 

 legs are comparatively slender and ineffective. The carapace in most of them however is 

 remarkably hard, and its arched form gives it additional power of resistance. 



The extreme minuteness of the eyes would agree with the idea of their lurking and 

 somewhat stationary habits ; and this, with the almost rudimentary form of the antennae, 

 appears quite inconsistent with any high development of the functions of relation. In 

 entire agreement with the view I have taken of the slow and feeble movements of these 

 animals, as deduced from a consideration of the structure of the organs of locomotion, is 

 the diminished extent of their respiration, evinced by the reduction of the number of their 

 branchiae to six pairs, whilst the foot-jaws and other manducatory organs are also small 

 and weak. 



Of the habits of most of the animals of this family we have no recorded history ; 

 but the account which that excellent observer Roux has given of the species of Ilia as 

 noticed by himself on the shores of the Mediterranean, is in exact accordance with the 

 structure I have described, and the functions which have been predicated from that 

 structure. Speaking of this genus, he says*, "Les Ilia ont le tet tres dur; ce sont des 

 Crustaces qui vivent solitaires, cramponnes parmi les Flustres et les Madrepores, ou sur 

 les 6cueils, a de moyennes profondeurs ; leur marche est lente ; ils manquent d'agilite* ; 

 la forme de leur corps et la debilite de leurs pattes s'opposent a ce qu'ils puissent nager ; 

 on ne les voit courir qu'a 1' aspect du danger." And of J. nucleus he says, " Ce decapode 

 est extremement timide ; il habite les moyennes profondeurs coralligenes, d'ou il ne sort 

 que lorsque le hasard lui presente quelque proie facile a saisir. II ne s'approche jamais 

 des rochers du rivage. On le rencontre rarement parmi les algues, si ce n'est en Mars, 

 epoque a laquelle la femelle vient quelquefois y deposer des oeufs qui 6closent en 6te\" 



The geographical distribution of the Leucosiada is as remarkable for the restriction of 

 the genera of which it is composed to special localities, as is the whole family with respect 

 to its zoological relations, which have already been considered. Every genus, without 



* ' Crustaces de la Mediterranee.' 



