17 Grust. 
CRUSTACEA. 
Suborder II. Reptantia. 
Fam. 1. Homaridce (^Astacus is intermediate between them and 
the Thalassinidce). 
Fam, 2. Eryonidce. 
Fam. 3. Loricata (Palinurus, Scyllarus). 
Fam. 4. Thalassinidce,. 
Fam. 5. Anomala (De Haan). 
(a) PaguroideUy inch Lithodes. 
(b) Galaieidce, inch Porcellana. 
(c) Hippidce. 
Fam. 6. Brachyura. 
(a) Dromiacea. 
(h) Genuina. 
The differences between the Natantia a,ud Reptantia Sive rather numerous. 
The more important of them are : — the articulation of the fifth and sixth 
joint of the legs being moveable only in one direction, a ginglymus, in the 
former, and turning round its axis in the latter ; the situation of the male 
orifice in the articular membrane between the thorax and fifth leg in the 
former, in the basal joint of the fifth leg in the latter ; the antennal 
scale being very large in the former, and small in the latter ; the body 
being compressed and horny in the former, depressed and calcified in the 
latter, &c. The extinct genera Udora^ Udorella, and Hefriga are. on 
account of the structure of the pleon, placed among the Eucyphota^ 
although the two former are provided with exopodites in the adult state ; 
Hoploparia, Eryma, Glyphcea, Pemphix. and Clytia among the Homaridce. 
The whole is written in Danish, but a general synopsis of the families, 
indicating their full characters, is given in Latin at pp. 155-160, and a 
detailed recapitulation of the whole in French, pp. 163-207. Dan. Selsk. 
Skr. (6) i. 2, pp. 25-210, 6 pis. 
The organs employed for keeping the gills clean are in Palcemon the 
first pair of thoracic feet ; in Alpheus and Hippolyte, probably the 
second ; in the Paguridee^ in Mglea and Hippa^ the last. These are aU 
remarkably slender and moveable, but not rudimentary, as was supposed. 
In the Brachyura,, internal appendages of the maxillipeds do the same 
service, their hairs are finely serrate, and are even as it were combed in 
'Trichodactylus by a row of pointed tubercles in the middle line of the 
gills. Fritz Muller, Kosmos, vii. pp. 148-152, with woodcuts repre- 
senting the hairs and tubercles ; abstract in J. R. Micr. Soc. hi. p. 631. 
BRAOTIYUBA. 
Boas describes at length the oral parts and legs of Carcinus mcenas, as 
typical for the whole Sub-order, and points out some differences regard- 
ing them in the types of other families, as Ocypode, Cardisoma, Grapsus 
Pseudocorystes, Dorippe,, Calappa, HepatuSy Persephone^ and Ranilia ; 
Dan. Selsk. Skr. (6) i. 2, pp. 141-147, pi. i. figs. 16-20 & 36, pi. ii. figs. 
66-68, pi. hi. figs. 96, 97, & 125-128 ; recapitul., pp. 201 & 202. He 
