280 MR. BELL, HORÆ CARCINOLOGICJE ; 
pedes in eodem plano inserti; orificia generationis masculina in sterno locata, feminina 
in medio artieulo tertio sterni; abdomen arctè cum sterno cohærens, operculiforme, in - 
maribus 4- vel 5-, in foeminis 5-articulatum ; abdominis articuli primi organa vaginæformia 
recta vel spiralia basi sejuncta in .Leucosiis, vel compressa basi conjuncta in Tliis; organa 
excitantia articuli secundi, aut tertiam partem anteriorum æquant in Leucosiis, aut plane 
desiderantur in Tliis et Philyris; appendices abdominales foeminarum externæ oblon 
foliaceæ et internæ setaceæ sub angulo recto geniculatze."' | 
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 Grapside and Ocypodide, 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 swimming, as in the Portunide, or still more in Matuta; 
nor is it fossorial, as in Carcinus and many others; nor suited for climbing, as in the long - 
slender-legged Leptopodiade ; nor for self-concealment, as in the Calappade. 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 antennæ, 
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 
branchiæ 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 Tlia 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 Tlia ont le têt très dur ; ce sont des 
Crustacés qui vivent solitaires, cramponnés parmi les Flustres et les Madrépores, ou sur 
les écueils, à de moyennes profondeurs; leur marche est lente; ils manquent d'agilité ; 
la forme de leur corps et la débilité de leurs pattes s'opposent à ce qu'ils puissent nager; | 
on ne les voit courir qu'à l'aspect du danger.” And of I. nucleus he says, “ Ce décapode 
. est extrémement timide; il habite les moyennes profondeurs coralligènes, d’où il ne sort 
que lorsque le hasard lui présente quelque proie facile à saisir. Tl ne s’approche jamais 
des rochers du rivage, On le rencontre rarement parmi les algues, si ce n'est en Mars, 
époque à laquelle la femelle vient quelquefois y déposer des œufs qui éclosent en été.” — 
y el distribution of the Leucosiade is as remarkable for the restriction of 
- s > which it is composed to special localities, as is the whole family with respect — 
gical relations, which have already been considered. Every genus, without 
= * “Crustacés de la Méditerranée,’ 
