118 ZOOLOGY. 



.^f'mus, fi<j. 5) live upon the coast, di<?ging holes several feet deep, where 

 there is not too mur.h sand to cause them to cave in, and some of the species 

 run so rapidly that a man can scarcely catch them. Ocypoda arenaria 

 inhabits the coast of the United States and the Antilles, digging a hole three 

 or four feet deej), just beyond the limit of the surf, whence it wanders in 

 search of food. According to Say, they hybernate at some distance from 

 the water, in a hole made for the purpose, the mouth of which they close. 

 Gelasi7nus roeans^ known on the United States coast under the name of 

 fiddler, has one of the anterior feet of the male much larger than the other, 

 the large one being indifferently upon the right or left side. 



Fam. 3. Cancridcp^ including the Portunidra and PilumnidcB of Leach, is 

 equivalent to the Cyclometojyes of Milne Edwards, and includes, under two 

 sub-families, most of the forms known under the name of crab. The sub- 

 families are : the CancerincB {Cancer^ pi. 78, ßgs. 1, 2) and the Portu- 

 nhue {Thalamita, fig. 3), which includes a great number of species under 

 various genera. They are found near the coasts a considerable number 

 together, and are taken for food. They feed npon living or dead animal 

 food, particularly upon decaying carcases. Some of them attain a large size, 

 PseudoGarcinas gigas being ten inches or more in diameter. The Portunince 

 correspond to Latreille's swimming Brachyura, and are distinguishable from, 

 the Cancerin?e by the posterior feet being flattened and adapted for swim- 

 ming, as represented in figure 3. In Zupa, the carapace is wider than long, 

 and has nine tooth-like projections on each side before. The common 

 edible crab of the Atlantic coast of the United States, has been described 

 as Lnpa hastata by Say, .Tour. Acad. ISTat. Sei. i. 05, 1817. It is abundant 

 in bays and inlets, feeds upon putrefying animal matter, and buries itself in 

 tlie sand to the eyes and antennae. The shell is generally cast in the spring, 

 when the animals are sought after under the name of soft crabs. 



Fam. 4. Maiidce. This family includes the thorny and sjiider-crabs, many 

 of which have long and slender feet. The epistoma, ©r region between the 

 mouth and antennte, is large and square ; the carapace is narrowed ante- 

 riorly, so as to give it a triangular outline, whence Latreille's names 

 Triangulares and Oxyrhinchi. The front is narrow, and generally extended 

 into a prominent rostrum ; the nervous system is more concentrated than 

 in any of the other Crustacea, and on this account it may be considered the 

 highest group among them. They are all marine, living at considerable 

 depths ; their motions are tardy, and they do not swim. As American 

 examples, Leptopodla calco.rata and Libinia üomalicidata., Say, may be 

 mentioned. There are two sub-families : Maiinm and Parthenopiinm. 



Class 4. AroAihnida. 



This class -includes the various articulate forms known as spiders, mites, 

 and scorpions, the characters of which place them between the Crustacea 

 and Insecta. In general, the head is not distinct from the thorax, but inti- 

 mately connected with it, forming a large segment named the cephalothorax, 

 322 



