412 



Div. 3. ARTICULATA.— CRUSTACEA. 



Class 1. 



THE FIRST FAMILY* OF DECAPODA,— 

 Decapoda Brachyura (KleisfagnaihOj 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 feraalesf, 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 

 incarryiiig 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 



Tig. l.~-Carcinu8 Manns IComxnou small Kdible Crab), upper aide and under Pyramidal platCS, COmpOSCd of a great nuni- 



■idc of tiie body, with the liiiilis truiicrttcd. — «, lateral antenna; 6, inter- \ r • a. ^ a j. Ji ^i 



mediate antennji; c, eye; d, outer loot jaw; f,y,^. A, base of the five pairs "^r 01 nimute leaflets SprCad OnC UpOn thC 

 of legs ; ft, tail; /, sternum. . ^ r • t- •^ ^ 



Other : the foot-jaws are ordinarily shorter 

 and broader than in the Decapods, the outer pair forming a kind of labium- 

 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, divisil)le into seven sections and a great numlter of minor divisions, regarded I)y recent authors 

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

 posed. The s])ecics thus characterized constitute the first five sections, Pinnipedes, Arcuata, Quadri- 

 latera, Orbiculata^ and Trigoua.J 



had \ouf^ perplexed Crustaceolo),;i8ts ; and M'Leay, in order to adopt 

 his (juiMnriHii hvstein l-i these animals, has divided ilie Ueeapoda itito 

 five tribes, Ti'ir«i(onostoina and 'I'rijfiinustonia (composin^j; tiie 

 Brachyura), and Anoiuura, Sarobranchia, and Car idea (composing 

 llie Macrttura). — Uluntr, Annulus. o/ South yfjricn. No. li.] 



* The groups thus indicated are founded upon a j;'-*"^'"'^' survey of 

 in^portant «nalnniic;il cliaracters, and g-enerally correspnnd with the 

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

 Kahricius. Tliese families are here of ^reati-r extent than in my 

 otlier "ritliiKH ; but if we rcffard tliese as primary ordinal diviniona, 

 and the |^roop>; here citlUd tribes as families, the arrani^'emenl nill be 

 found esseiilially identical. In the same manner the subt;enera here 

 Indicated oujjlit, in a more di tailed arran^ijemcnt, to bt rci^arded as 

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

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

 level of our present knortledj^e, and in order to diminish the vast 

 number ol sub-yenera, to lonvert the aectiona into tribes or genera, 

 which might then be di\idi-d Into subgenera. 



t The a[)pareiit number of segments is generally seven, varying 

 occasionally in the sexes of the same species, in which case the 

 females have the Ita^t number. Dr. Leach made great use of this 

 ch:irHcter, but it appeals to me to be too unimportant. 



t [l.atreille regarded this arrangement of the Crabs here given as 

 artificial in niany respects, and he had modified it not onK' in his 

 h'amillra NnturrUea, In which the tribes here given were introduced 

 but their relative pr>sition altered, but in his subsequent C'uurs 

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

 follows : — 

 Section 1. Homocheles, claws of equal sire in both sexes. 



Uivivion 1. All the feet attached to the body In the sam; line. 



Tribes.— 1. Wuadrilatera. 'i. Arcuata, 'A. Pinnipedes, 4. Christi- 

 maiii, 5. Cry)plopoda, 



Division 2. With the two or four posterior legs dorsiil. 

 Tribe. — C. Notopoda. 



Seetion 2. Iletcroeheles, claws of the males larger than those of llie 

 females. 

 Division 1. All the legs in the same line. 



Tribes.— r. OrbicuLita, S. Trigona. 

 Division 2. Hind p;iirs of legs very small, and either dorsal or 

 abortive. 

 Tribe.— 9. Hypopthalma. 



Dr. Leach, as above mentioned, adopted the number of abdomina* 

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

 more numerous families. Milne Kdwards, however, in his His*. Nut. 

 drs Cruitavht now in course of publication, has, from anatomical 

 considerations, considered it more natural to separate the Brachyura 

 into only four great families. 



1. The Oxyrhycha ( IVigona, Latr. or the families Maiadcc, Lithodiadie, 

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

 backed crabs, the legs being long, tht carapax narrowed into a point 

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

 Macropodiens, Maiens, and Parthenopiens). 



2. The Cycloiiietopa (or the Canceiidtc, Portunidse, and Ptiumnidas 

 of Leach) ^ carapax very large, arched in front, narrowed behind, legii 

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

 1. Can<enens, composed of three sub-tribes, Cryptopodu, Arcuata, 

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



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

 rilateral or ovoid, the front transverse and Unotied, cpisloma very 

 short. 



4. The Oxystoma (CorystiJtc and Leucosiadae, Leach), with the shell 

 orbicular and arched in front, which is not poined, epistoma ob 

 solcte. 



