176 CRUSTACEA. 



The most common species — Cancer ruricola, L., Herbst., Ill, 

 36, when yoimg, IV, xx, 116; xlix, 1, is of a more or less lively 

 blood-red colour, more or less extended, and sometimes spotted 

 with yellow with a deeply marked impression of the letter H. 

 It is the Crahe violet, and Crabe peint of travellers ; the name 

 of Tourlourou appears to me to be more peculiarly applied to this 

 species *. 



Sometimes the shell is nearly square, subisometrical or not, broader 

 than it is long-, flattened, and the front turned down for nearly the 

 whole of its width. The ocular pedicles are short and inserted at tlie 

 anterior lateral angles. The two ordinary divisions of the interme- 

 diate antennae are very distinct. The inner sides of the exterior foot- 

 jaws are separated, leaving an angular space between tliem ; their 

 third joint is almost as long as it is broad. The claws are short and 

 thick, and the other feet very flat; the fourth pair, and then the third, 

 are longer tlian the others ; tarsi spinous. 



Plagusia, Lat. 



The mediate antcneae lodged in two longitudinal and oblique fissures 

 traversing the whole thickness of the middle of the clypevis f . They 

 are inferior or covered l)y this part in 



Grapsus, La77i. 



Where the shell is somewhat wider before than behind, or at least 

 not narrower, while in the Plagusise it widens from before back- 

 wards. 



The Grapsi are found throughout all parts of the globe, but are 

 more particularly abundant in the vicinity of the tropics. They are 

 not seen in Europe beyond 50 deg. of latitude. If I mistake not they 

 are called Ceriques at Martinique. Marcgrave has figured some 

 Brazilian species by the name of Aratu, Aratu-pinima (Grapsus 

 cruentatus, Lat.) and Carava-una. At Cayenne they are called 

 Ragabeumba, or soldier. 



These animals conceal themselves during the day under stones, 

 &c., at the bottom of the sea. I have been informed that some of them 

 even climb up the trees on its shores and hide beneath their bark. 

 The broad and flattened form of their body and feet enables tliem to 

 support themselves for a moment on tlie surface of the water ; they 

 always walk sideways, sometimes to the right, and ;:t others to the 

 left. Certain species inhabit rivers witliin the bounds of tide water, 



* See the article Tourlourou in the Encyc. Methodique. Messrs. Audouin and 

 Edwards have lately communicated to the Acad. Roy. des Sc, some very curious 

 remarks upon an organ peculiar to these animals, which form a sort of reservoir 

 capable of containing a certain quantity of water, and placed immediately above 

 the branchiae. This accounts for the unusual convexity of the anterior sides of their 

 thorax. 



t P. depressa, Lat. ; Herbst., Ill, 35 ; — P. clavimana, Lat., Herbst., lix, .3 ; 

 Desmar., Consider., XIV, 2. The tail appears to me to consist but of four distinct 

 segments. The third, however, presents one or two deep and transverse lines. In 

 the Grapsi there are seven segments, the third of which has an angular dilatation on 

 each side of its base. 



