114 ZOOLOGY. 



seven segments, the first pairs of feet are well developed, and used in 

 prehension, and the five succeeding pairs are ambulatory. Orchestia {pi. 



Fam. 2. Ilyperinidm. Aiicylomera {fig. 19). These are generally 

 parasitic upon fishes and medusae. They swim well, but walk badly. 



Okder 9. SxoMAToroDA. Branchise abdominal and free, not afiixed to 

 the sides as in the Decapoda; abdominal appendages well developed. The 

 shell is delicate and transparent, the thoracic carapace is large ; and the 

 body bears some resemblance to that of a lobster, being semi-cylindric, 

 rounded above, and flat beneath, and the posterior extremity is obtuse and 

 spinose. The large and conspicuous arm-like organs, which resemble the 

 raptorial anterior feet of Mantis {pi. 80, fig. 90), present a remarkable 

 character, and are doubtless used in taking their prey. The last articulation 

 closes upon the previous one like the blade of a knife into the handle, and it 

 is well ada^^ted for holding. These organs correspond to the second pair of 

 foot-jaws in the lobster and crab, and to the first pair of thoracic feet in the 

 Isopoda. The oval laminated organ in front of these is an appendage of 

 the second or external pair of antennae. The last segment of the abdomen 

 and the appendages of the sixth segment, form a caudal fin used in swimming, 

 assisted by the three posterior pair of thoracic feet. Squilla {pi. 78, fig. 

 15); GonodactyluH {fig. IG). Gonodactylus chiragra inhabits the Mediter- 

 ranean, the coasts of the Seychelles, America, Trincomalee, and Tongatabu. 

 The order contains the two families, EncJdldidm and Sg^uillidce. 



OiiiJEit 10. Dii'Loi'ODA. This is usually included with the preceding, though 

 Milne Edwards separates it as a distinct order, but without assigning to it 

 a systematic name. That here chosen is in allusion to the appendages of 

 •the feet, which give them the appearance of being double. It is an order 

 •of small extent, of which Phyllosoma {pil. 78, fig. 17) is the type. The 

 eyes are placed upon peduncles, the abdominal appendages are rudimentary, 

 the branchia3 wanting, the body broad, thin, and scale-like, corajiosed of a 

 large cephalic shield, and a smaller thoracic one bearing the feet upon 

 •extensions of its margin. These animals are translucent, and so thin that 

 it is difficult to perceive how there can be room for the internal organs 

 between the up]ier and lower surface. In Phyllosoma the mandibles are 

 large ; the first and second pairs of mandibles, and first pair of foot-jaws, are 

 small, and the second pair of foot-jaws are not raptorial. The feet are long 

 and slender, and provided with palpiform appendages ; and from the .ease 

 with which the feet are lost from the point where the appendage is attached, 

 they are seldom seen perfect, so that the latter appears to be the true 

 termination of the foot. The first pair of feet are small, and without a 

 terminal nail, and generally without an appendage. The last pair are often 

 rudimentary. The abdomen is sometimes confounded with the thorax, and 

 at other times rudimentary. 



Okdek 11. Decapoda. The individuals of this order, as the name implies, 



liave ten ambulatory feet; the branchiae are placed in lateral cavities 



beneath the sides of the large carapace ; the head is immovable ; the mouth 



has numerous organs between the mandibles and first pair of feet ; and the 



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