AMPHIPODA, 
219 
Dictylocera, Lat. 
The body not thickened anteriorly; the head moderate, depressed, 
nearly square ; eyes small ; four extremely short antennae composed 
of but few joints, as in Phrosine, of various forms — the inferior being 
thin and styliform, and the superior terminated by a small concave 
plate on the inner side — resemble a spoon or forceps 
The others — G ammarin^, Latr. — always have four antennas ; their 
body, invested with coriaceous and elastic segments, is generally 
compressed and arcuated ; the jjosterior extremity of the tail is de- 
prived of fins; its appendages are styliform and cylindrical, or conical. 
At least two of their four anterior feet are usually terminated by a 
forceps. 
The vesicular bursae, in those where they have been observed — 
the Gammarinae, Latr. — are situated at the exterior base of the feet, 
commencing with the second pair, and are accompanied by a small 
plate. The pectoral scales which inclose the ova are six in number. 
Sometimes the four antennae, although of different i^roportions in 
several, have a similar form and use ; the inferior have no resem- 
blance to feet nor do they perform their functions. 
A subgenus which we have established under the denomination of 
loNE, Lat., 
Only, however, from a figure given by Montagu — Oniscus thora- 
cicus, Trans. Lin. Soc., IX, III, 3, 4 — exhibits very peculiar charac- 
ters which separate it from all others of the same order. The body 
consists of about fifteen joints, but only distinguished by lateral 
tooth-like incisions. The four antennae are very short ; those that 
are external, being longer than the others, are the only ones visible 
when the animal is seen on its back. Each of the two first segments 
of the body of the female is provided with two elongated, fleshy, 
flattened cirri resembling oars. The feet are very short, concealed 
under the body and hooked. The six last segments are furnished 
Avith lateral, fleshy, elongated, fasciculated appendages, which are 
simple in the male and like oars in the female. At the posterior 
extremity of the body Ave also observe six simple, recurved appen- 
dages, tAVo of Avhich are larger than the others. The alidominal 
valves are very large, cover the Avhole inferior surface of the body, 
and form a sort of receptacle for the ova. This animal remains con- 
cealed under the shell of the Calinassa subterremea, on the side of 
Avhich it forms a tumour. Montagu, having AvithdraAvn one of these 
Crustacea from its domicil, kept it alive for several days. The female 
is ahvays accompanied by the male, Avho fixes himself firmly to her 
abdominal appendages by means of his forceps. It is a rare animal 
Avhich, in its habits, approaches the Bopyri f. 
All the ensuing Amphipoda have the segments of the body iierfcctly 
distinct, throughout their av hole extent; in neither sex nor in any 
* Phros. seminulufu, Risso, Ib. ; Desmar. The stem of the inferior antennae consists of 
two or three joints, while in PLrosinc it is inarticulate. There also, the joints of the 
peduncles of the same antenna; are shorter. 
t See Ann. clcs Sc. Nat., Decemb. 1826, XLIX. lo, the male — 1 1 , the female. 
