DECAPODA. 



413 



The first section, Pinni pedes, have the hind pair of legs terminated hy a flattened plate for swimming, 

 and these species are accordingly met with at a distance from the coasts. 



Amongst these swimming or shuttle-crabs, as they are termed, are especially to be noticed the exotic species, 

 composing the genus Matuta, Fab., having the carapax nearly circular, and armed on each ride with a strong spine, 

 and with the four posterior pairs of legs terminated by a dilated plate for swimming. The same is also the case, 

 but less strongly, in Leach's genus Polybiui, consisting of the single species, /'. HeiuloieH, found on the Devon- 

 shire coast. Amongst the species with only the last pair of leq;s dilated at the extremity into a plate for swim- 

 ming, the genus Orithiiia, Fabr.. consisting of a single Chinese species, is distinguished by the tail of the males 

 being distinctly seven-jointed, whereas there are only rive joints in the males of all the other 1'innipedes, the females 

 alone having seven joints. Amongst these the genus Pmlojilhalmus, Lamarck, has the carapax transverse, and 

 armed at each side with a very long spine ; the ocular peduncles are very long (/'. ipinotut, Latr., Isle of France) ; 

 Others which have the ocular peduncles short, and which are of the ordinary crab-like form, compose the genus 

 Portunui, Fab., amongst which may be mentioned Cancer pu'-ei; Linn., and Cancer MatUU, Linn. (Curriniis 

 Mamas, Leach), two small species, commonly used as articles of food by the lower orders in Ixmdon. The last- 

 named species is exceedingly abundant ; the terminal joint of the hind legs is much narrower than in the preced- 

 ing groups, and thus this species forms a passage to — 



The second section, Arcuata, in which the tarsus, or last joint of all the legs, is conical, and some- 

 times compressed, hut never forming a swimming plate, and the carapax arched in front and narrowed 

 behind, with the claws of equal size in both sexes, and the tail is composed of the same number of 

 nenta as in the Portuni. The true Crabs, composing the restricted genus Cancer, Fabr., are the 

 types of this section, and are distinguished by having the third joint of the outer foot-jaws emarginate 

 or sinuated near the inner extremity, and nearly square. The antennae scarcely extend beyond the 

 front, with but few joints, and are folded backwards. 



Cancer pagurtu, Linn., the common large edible crab, has the carapax very broad, and arched for a great dis- 

 tance along the sides, each side having nine festoons, and the middle in front with three short teeth : the claws 



are larje, and the fingers black and armed with obtuse 

 points. It sometimes reaches nearly a foot in breadth, 

 and is of common occurrence on the coasts of England 

 ami France. [It is captured by sinking pots, baskets, 

 or nets, baited with decaying animal matter, to a con- 

 siderable depth in the ocean, alonp^ the rocky coast. 

 During the summer months it is very abundant, especi- 

 ally where the water is deep; and at low tide they are 

 found in holes of rocks in pairs, male and female, and if 

 the male be taken away another will be found in the 

 hole at the next recess of the tide. By knowing this 

 fact, an experienced fisherman may twice a day take 

 with little work a vast number of specimens, after hav- 

 ing discovered tbeir haunts. In the winter they are 

 supposed to burrow in the sand. OT to retire to the 

 deeper parts of the ocean. (Ent. Compend. p. 86.) Mr. 

 Hell has described seme beautiful exotic species of this 

 genus in the Transactions of the Zoological Society, 

 vol. I.] The genua Xaniho, Leach, is nearly allied tothe 

 preceding, but having the external antenna- short, and 

 inserted in the external canthus of the eye. The typical species, X.florida, Leach, inhabits our coasts. 



The genus Perimela, Leach, has a longer carapax, with the edges stromrly toothed, the i ight hind legs equally 

 compressed, and longer antennae. P. denttculata, Leach, occurs in various parts of our coast, and in the Medi- 

 terranean. 



The ' Uu, Leach, has the carapax nearly rounded, and dentated at the sides, the tail narrower than 



in the preceding; the lateral antenna elongated, the claws very strong, and rather short. The t > |><- of this 

 genua Is the Cancer 1-dentatueot Montague, by whom Itwas discovered on the coast of Devonshire. Other 

 genera, which it would occupy too much space to notice, have been separated by Leach, Latreille, and others. 

 Amongst them, however, the two exotic genera, Mwreea, Leach. KoAHePatue, Lat., are distinguished b> their 

 claws being greatly < d, so that the] have subsequently been separated bj Latri 



na d Cristimani, or crested-handed Crabs. 



Flfr Si—Canetr Pagunu, Linn., with the mil of the male, a; ind ol 

 the female, b. 



Mr. M'l..-nV» arrangement ..f the tlrai hrura. ». R iv,-n in the 3rd - . ,, . , r . , i Shell ireualr.l.nith Ihr , 



in of the IHutnttou of lb* Zoology of southern Abie*, Jut nub- I < -*" cr ' n * l Arcn,u <-""■) -J fci .. tJ ( 



J Shrll uiir>rn, «lth 



Aaaloglu. Tribe TriKono,tom». 



Shrll ..r o ;,,». 



Shell quadrilateral | ;>i ua. 



I, u u follon 

 Tritir TrtngoiMMtono, 



Pi tl..r;rii l'ir ..it. Crabt) 



GnpiilM Square Cr»bi) 



, 



| I •1»|.|.|C, 



Inac 



iar.andl 

 Mr. (TrlamuLr Crab.) \ ^ 



