660 CLASS X. ; 
others, as Orchestia littorea, under the name of Cancer pulex, Syst. nat. ed. 
12, I. p. 1055). 
Gammarus pulec Fasr., GERV. is very common in ponds. The female 
carries her eggs under the body at the base of the feet, until the young 
emerge. RaseEL saw the animals nibbling at roots, fruits, and other parts 
of plants which he gave them. Usually, however, they live on animal 
food, and according to Dr GEER, do not spare even the bodies of their 
companions. They attain a length of about 2”. The hinder end of the 
body is always bent downwards. Compare also on this species J. C. 
ZENKER De Gammari pulicis Fasr. Hist. naturali et sanguinis circuitu 
commentatio. Accedit Tab. en. Jenz, 1832, 4to, and, on the difference of 
the two species, GERVAIS Ann. des Se. nat. 2e Série, Iv. 1835, Zoologie, 
pp. 127, 128. 
Orper LX. Stomatopoda. 
Two compound eyes, placed on a biarticulate moveable petiole. 
Antenne four, placed nearly in the same horizontal row; internal 
long, terminated by two or three multiarticulate sete, external 
mostly furnished at the base with an oval ciliated lama. Feet of 
trunk mostly in seven or six pairs, more rarely eight. Mouth 
inferior, often situated between the bases of anterior feet. Branchize 
mostly adhering to the caudal feet, more rarely to the thoracic, never 
covered. Tail mostly terminated posteriorly by a foliaceous pinna. 
Shell thin, in many almost membranous. 
Family XXIV. Unipeltata. Body elongate, narrow. Cephalo- 
thoracic shield elongate, often produced over the back of the ante- 
rior segments of trunk. Anterior segment of cephalothoracic shield, 
bearing the middle antenna and eyes, distinct. One pair of max- 
illiform feet slender, elongate. Seven pairs of feet in trunk or 
thorax; first pair large, with last joint mostly falcate, dentate in- 
ternally; second, third and fourth pairs shorter, approximate to 
mouth, terminated by an oval hand and moveable hook; three last 
pairs slender, remote, mostly furnished with a styliform appendage. 
Of caudal feet six pairs; the first five mostly bearing branchie of 
1 From a passage in the Fauna Suecica p. 246 ‘‘habitat ad littora maris vulga- 
tissimus” it would seem, that LINN&US probably by Cancer pulex had a species in view 
different from Gammarus pulex or fluviatilis, perhaps Gammarus locusta FABR.; that 
he also confounded Orchestia with it appears, however, from his citation of BASTER, 
Hence it is impossible to quote with justice Cancer pulex L. as a synonym of a 
determinate species. : 
