114 ZOOLOGY. 
seven segments, the first pairs of feet are well developed, and used in 
prehension, and the five succeeding pairs are ambulatory. Orchestia (pl. 
78, jig. 18). aa: 
Fam. 2. Hypermide. Ancylomera (fig. 19). These are generally 
parasitic upon fishes and meduse. They swim well, but walk badly. — 
Orver 9. Stomatopopa. Branchiz abdominal and free, not affixed 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 Yesemble the 
raptorial anterior feet of Mantis (pl. 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 adapted 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 antennz. 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. Squzla (pl. 78, fig. 
15); Gonodactylus (fig. 16). Gonodactylus chiragra inhabits the Mediter- 
ranean, the coasts of the Seychelles, America, Trincomalee, and Tongatabu. 
The order contains the two families, Hrichthiide and Squillide. 
Orver 10. Diretopopa. 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 (pl. 78, fig. 17) is the type. The 
eyes are placed upon peduncles, the abdominal appendages are rudimentary, 
the branchize wanting, the body broad, thin, and scale-like, composed 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 upper 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. 
OrpER 11. Decaropa. The individuals of this order, as the name implies, 
have ten ambulatory feet; the branchiz 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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