DECAPODA. 415 



•ni«l ciliated. Tlie tail is composed of seven segments, but three of them are confluent in the males. The type 

 !s Cancer pertonatus, Herbst., found upon the coast of England. [This genua is of very difficult location, and has 

 little nal relation with Leueotla: it is more nearly allied to some of the arcuated species.] 



Leucoxia, Fab., has the carapax of variable form, but generally globular or ovoid, and as hard as stone; the 

 lateral antenna; and eyes are very small ; the tail, large and suborbicular in the females, is generally composi d of 

 lour or five, but never of seven segments. Dr. Leach cut up this genus into many others. A very few species 

 belonging to his genus Ebalia are found on the English coast. The majority of the family inhabit tropical seas. 



The fifth section, Trigoxa, is of very great extent, and consists of species having the carapax 

 generally irregular or suboroid, and narrowed in front into a kind of beak ; ordinarily very rough Bad 

 uneven, with the eyes lateral. The epistoma, or space between the antennae and oral cavity, is always 

 nearly square, and as long as broad. The claws, at least of the males, are always large and long. 

 The following legs are very long in the majority, and occasionally the posterior pair have a form dif- 

 ferent from the preceding. The apparent number of joints in the tail varies, being seven in both sexes 

 of the majority of species ; but in others, at least in the males, it is less. Many of these crabs are 

 commonly called sea spiders. Although the number of species of this section are very numerous, only 

 two had been discovered in a fossil state ; one of which, Maia Squinado, exists at the present time in 

 the same localities. 



Latreille divides this section into sub-sections, from the number of joints in the tail, and the form of the joints of 

 the foot-jaws. Amongst those with the tail, either in both sexes, or in the females, composed of seven segments, 

 '.'urthi-nnpe, Fabr., is distinguished by the immense size of the claws, and the smallness of the other legs; the 

 fingers are suddenly bent downwards, the ocular peduncles very short, and the carapax exceedingly rough. 

 A species found on the coasts of England and France (Cancer a-sper, Pennant) forms the genus Eurynume, Leach : 

 the tail is seven-jointed. The other species of Parthenope are found in the Indian ocean. 



Maia, Leach, has the lingers not detlexed ; the anterior pair of legs scarcely thicker than the others, which are 

 moderately long ; the carapax has two frontal spines, and its back and sides are also armed with many tubercles 

 and spines. The typical species, Cancer Squinado, Herbst., is very common on the coasts of France and the 

 Mediterranean. It is one of the largest of our crabs, and was known to the ancient Greeks under the name of 

 Maia, being sometimes figured on their medals. [My the fishermen it is called the Thorn-back, or King Crab.] 

 Another common British species is the Cancer araneus, Lin., belonging to Leach's genus Hyat, having the 

 carapax elongate, SUbtriangular, subtuberclcd, with the lateral margins dilated into a lanceolate projection, ex- 

 ternal antennas with the first joint dilated. 



Amongst the species, which have not more than six abdominal segments, and the legs generally long and 

 [inform, and the third joint of the outer foot-jaw narrower than in the preceding subsection, Efgmenoeama, 

 Leach, has the carapax triangular or orbicular, depressed [and soft], and the basal joint of the lateral autennae 

 does not reach beyond the ocular peduncles. The species are small, and found in the Indian and Australian seas. 

 The British genera, Innchux and Acfueux, have the carapax subconvex and triangular, and their abdomen six- 

 jointed. Their four pair of posterior legs are very long, especially the pair succeeding the claws. In the latter 

 respect the British genus Stenorhynchut, Latr. {Maaropodia, Leach), closely tesembles them, ha\ ing al m the tail 

 .^ si\-joii,ted in both sexes, and the front of the carapax notched. The type is 



the very common Cancer Phalangimn, Pennant. The gem;- Pactolus, Leach, 

 characterized by having the four hind-legs furnished with a didactyle chn [has 

 been found by M. Milne F.dwards to have been construe ted upon a fictitious speci- 

 men in the British Museum]. 



IAihodet, Latr., is at once distinguished by having the hind pair of Legs so sn all 



as to appear almost abortive. The type is a large crab of rare 0CCU1 rence in British 



seas, named Cancer Main, Linn. The tail is membranous j the outer IbOt-jawS an 



.ited and apart ; the carapax is triangular, very spinous, and terminated in a 



toothed spine. [This is a very anomalous genus, whose relations are difficult to 



, — Stenorynchoi Pluliii^ium. decide. T 



[Professor Bell and lie lUau have described many new and curious genera belonging to the section Trigonax 

 the former, in the second \olume of the Transactions of the Zoological Society ; and the latter, in his work upon 

 Of Japan.] 



The sixth section, Cryptopoda, is composed of a few species remarkable for having the l< 

 except the anterior pair, concealed, when folded up, beneath the dilated lateral margin of the carapa\, 

 which is Dearly cither semicircular or triangular; the upper edge of the claws is compressed, and 



formed like a cock's comb. The species are exotic, and compose the two genera l Pahr., and 



J'lhra. Leach. In the shape of their claws tlu\ resemble some of the Arcuatn and PttttUpedet, -och as 



Hepatui, Murtia, dec. ; so that tins section should be placed higher in the u riea. I hum maj alas 

 be said with respect to the ipeeiet of the following section, some of which approach the Arcmata, and 

 others the Orbiculata and 7Woono. 



