412 



CRUSTACEA. 



THE FIRST FAMILY* OF DECAPODA,— 

 Decapoda Brachyura {Kleistagnatha, Fabricius), — 



Has the tail (or post-abdomen) shorter than the thorax, without appendages or swimmerets at its 

 extremity, and in a state of rest folded beneath the breast, and lodged in a sternal cavity. 



It is triangular in the males, but rounded 

 and swollen in the femalesf, and is furnished 

 in the former with four or two appendages at 

 the base [on the inside], whilst in the female 

 it has four pair of double filaments employed 

 in carrjdiig the eggs, and which are analogous 

 to the swimming sub-abdominal appendages of 

 the Macrura. The antennae are small ; the 

 intermediate pair, generally lodged in a cavity 

 beneath the fore-margin of the carapax, are 

 terminated by two very short [articulated] 

 filaments. The peduncles of the eyes are 

 larger than in the Macrura. The first pair of 

 legs is terminated by a claw. The branchiae 

 are arranged in a single row in the form of 

 pyramidal plates, composed of a great num- 

 ber of minute leaflets spread one upon the 

 other : the foot-jaws are ordinarily shorter 

 and broader than in the Decapods, the outer pair forming a kind of laljium. 

 This family may be regarded as constituting the single genus 



Cancer, — 

 Comprising the numerous species of crabs [and consisting of a portion only of the Linnaean genus 

 Cancer, divisible into seven sections and a great number of minor divisions, regarded by recent authors 

 as genera]. Of these the majority have the legs attached at the sides of the breast, and always ex- 

 posed. The species thus charactei'ized constitute the first five sections, Pinnipedes, Arcuata, Quadri- 

 latera, Orbiculata^ aud Trigona.J 



Fig. 1 



(/, outer foot jaw ; tf,/, g-, A, base of the 



had long perplexed Crustaceologists ; and M'Leay, iu order to adopt I 

 his quinarian system to these animals, has divided the Decapoda into 

 five tribes, Tetrrtgonostoina and Trigouostoma (composinfj the 

 Brachyura), and Anomura, Sarobranchia, and Caridea (composing 

 the Macruura).— //;«sfr. AimiiUts. oj South Afrim, Xo. 3.] 



* Tlie groups thus indicated are founded upon a general survey of 

 important anatomical characters, and generally correspond with the 

 Linnsean genera, and sometimes also to those of the earlier works of 

 Fabricius. These families are here of greater extent than in my 

 otlier writings ; but if we regard these as primary ordinal divisions, 

 and the groups here called tribes as families, the arrangenaent will be 

 found essectially identical. In the same manner the subgenera here 

 indicated ought, in a more detailed arrangement, to be regarded as 

 genera, and thus, although the Decapoda are here only divided into 

 two genera, it would be correct, in order to bring the system to the 

 level of our present knowledge, and in order to diminish the vast 



o convert the sections into tribes or genera, 



■ided into subgenera. 



3cr of segments is generally seven, varying 

 same species, in which case the 

 females have tlie least number. Dr. Leach made great use of this 

 chnracter, but it appeals to me to be too unimportant. 



X [L.-itreille regarded this arrangement of the Crabs here given as 

 artificial in many respects, and he had modified it not only in his 

 Families Naturelles, in which the tribes here giver) were iutroduced 

 but their relative position altered, but in his subsequent Coins 

 d'Eutvmologie he proposed ano her arrangement of the order, as 

 follows :— 

 Section 1. Homocheles, claws of equal size in both se.\cs. 



Division 1. All the feet attached to the body in the same line. 



Tribes.— 1. Quadrilatera, 2. Arcuata, 3. Pinnipedes, 4. Christi- 

 mani, o. Cryptopoda, 



ub-ye 

 which might then be 



t The apparent number of set 

 occasionally in the sexes of t\xe 



Division 2. Wilh the two or four posterior legs tiorsiil. 

 Tribe.— 6. Notopoda. 



Section 2. Heterocheles, claws of the males larger than thoic of the 

 females. 

 Division 1. All the legs in the same line. 



Tribes.— 7. OrbicuUta, 8. TrJgona. 

 Division 2. Hind pairs of legs very small, and either dorsal or 

 abortive. 

 Tribe.— 9. Hypopthalma. 



Dr. Leach, as above mentioned, adopted the nuaiber of abdominal 

 segments, and was consequently led to distribute this order into -still 

 more numerous families. Milne Edwards, however, in his His*. Nat, 

 des Crustucis, now in course of publication, has, from anntumical 

 considerations, considered it more natural to separate the Brachyura 

 into only four great families. 



1. The Oxyrhycha (Trigon.i, Latr. or the families Maiadae, Lithodiadie, 

 and Macropodiadae of Leach), consisting of the sea spiders or thorn- 

 bacUed crabs, the legs being long, tht carapa.\ narrowed into a point 

 in front, the epistoma very large and nearly square. (Three triDes, 

 Macropodiens, Maiens, and Parthennpiens}. 



2. The Cyclometopa (or the Canceridae, Portunidae, and Pilumnidic 

 of Leach); carapa.v very lari^e, arched in frunt, narrowed behind, legs 

 moderately long, epistoma very short, transverse. (Two tribes, 

 1. Canceriens, composed of thrte sub-tribes, Cryptnpoda, Arcuata, 

 and Quadrilatera ; and, 2. Portuniens or Pinnipedes). 



3. The Catametopa (Ocypodiad^, Leach), having the carapax quad- 

 rilateral or ovoid, the front transverse aud knotted, epistoma very 

 short. 



4. The Oxystoma (CorystidiE and Leuco^iadae, Leach), with the sliell 

 orbicular and arched iu front, which is not poin-ed, epistoma <ib- 

 sulcfte. 



