ORDER AMFHIPODA. 
207 
The second, Gammarin^e, Lair ., have always four an- 
tennae ; the body is invested with coriaceous elastic tegu- 
ments, and generally compressed and arched ; the posterior 
extremity of the tail is without fins ; its appendages are in 
the form of cylindrical or conical styles ; two at least of their 
four anterior feet are most frequently terminated in a pincer. 
The vesicular pouches, in those in which they have been 
observed, are situated at the external base of the feet, be- 
ginning from the second pair, and accompanied by a small 
lamina. The pectoral scales enclosing the eggs are six in 
number. 
Sometimes the four antennae, although of different propor- 
tions in many, have essentially the same form and the same 
uses. The inferior do not resemble feet, nor perform their 
functions. 
One subgenus, which we have established under the deno- 
mination of 
IONE, 
After a figure of Montagu’s ( Oniscus thoracicus , Linn. Trans. 
JX. iii. 3, 4.) presents us with very peculiar characters, and 
which remove it from all the others of the same order. The 
body is composed of about fifteen articulations, but distin- 
guished only by lateral incisions, in the form of teeth ; the 
four antennae are very short ; the external, longer than the 
two others, are alone visible, when the animal is observed at 
the back ; the first two segments of the body are each provided, 
m the female, with two elongated cirri, fleshy, flatted, and 
similar to oars ; the feet are very short, concealed under the 
body, and hooked ; the last six segments are provided with 
lateral appendages, fleshy, elongated, fasciculated, simple in 
the male, branchy in the other sex. We also see at the pos- 
terior extremity of the body, six other simple, curved ap- 
pendages, two of which are larger than the others; the abdo- 
