280 MR. BELL, HORyE CARCINOLOGICE ; 



pedes in eodem piano insert! ; orificia generationis masculina in sterno locata, foeminina 

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

 maribus 4- vel 5-, in foeminis 5-articnlatum ; abdominis articuli primi organa vaginseformia 

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

 excitantia articuli secundi, aut tertiam jmrtem anterioriun sequant in Leucosiis, aut plane 

 desiderantm' in Iliis et Fhilyris ; appendices abdominales fceminarum externse oblongse 

 foliacese et internae setacese sub angulo recto geniculatse." 



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 efiergetic 

 movements such as belong to the GrcqisidcB and Ocj/podidce, in which these powers are 

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

 nor does it afford any means of swi mmi ng, as in the Portunidce, or stiU more in Matuta ; 

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

 slender-legged Leptoiwdiadce ; nor for self-concealment, as va. 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 antennse, 

 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 sis 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 Eoux has given of the species of Ilia as 

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

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

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

 Crustaces qui vivent soHtakes, cramponnes parmi les Jplustres et les Madrepores, ou sur 

 les ecueils, a de moyennes profondeurs ; leur marche est lente ; ils manquent d' agility ; 

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

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

 est extremement timide ; il habite les moyennes profondeurs coralligenes, d'oii 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 eclosent en et^." 



The geograpliical distribution of the Leucosiadce is as remarkable for the restriction of 

 the genera of -n^hich it is composed to special localities, as is the whole family vdih. respect 

 to its zoological relations, which have ah-eady been considered. Every genus, without 



* ' Crustaces de la Me'diterrane'e.' 



