668 ARTHROPODA SUB-KINGDOM VII 
Sub-Order A. AMPHIPODA. Latreille. 
Body laterally compressed, with gills borne on the bases of the walking feet ; abdomen 
elongate, the three anterior feet natatory, the rest posteriorly directed and saltatory. 
The Amphipods, or beach fleas, are mostly small, aquatic animals, and generally 
marine. They live in shallow water between rocks, beneath seaweed, ete., or in some 
cases in tubes or burrows constructed by themselves. They leave 
tracks upon the surface of mud and sand which resemble the 
Palaeozoic Nereites. Fossil remains are extremely scarce, and are 
derived chiefly from fresh-water strata. 
A few Palaeozoic forms have been described under the names 
of Necrogammarus Salweyi, Woodw., from 
the Ludlow beds; Diplostylus Dawsoni, S 
Salter, from the Carboniferous of Nova 

Fig. 1405. Scotia; Palaeorchestia, Zitt. (Fig. 1405), AM fe 
ae oe ee from the Coal Measures; and Bostrichopus, 
ae Lisek, near Beraun, Goldf., from the Culm Measures of Herborn. Fic. 1406. 
Patecl. /1 (@fter hese are all problematical forms of doubtful _ Gammarus Oeningensis, 
alivta Hae if ce ee ac Heer. Miocene; Oenin- 
relationships. ess uncertain 1n 1ts positlon gen, Baden. 2/;. 
is Acanthotelson, Meek and W., from the Carboniferous of Illinois, 
which, although raised by Packard to ordinal rank (Syncarida, see above under 
Schizopoda), shows no features incompatible with Amphipod 
relations. The few Tertiary forms, such as Gammarus, Fabr. 
(Fig. 1406); Typhis, Risso; and Palaeogammarus, Zadd., closely 
resemble living types. 
Sub-Order B. ISOPODA. Latreille.! 
Body depressed, usually broad, flat below, rounded above ; 
with seven free thoracic segments, and no strongly developed 
carapace. (Gills borne on the lamellar appendages of the abdomen, 
which is short-ringed and often reduced, its 
segments partially fused. Caudal segment 
relatively large, shield-shaped. 
Most Isopods are marine, frequenting 
the coast; a few inhabit fresh water, and 
about an equal number (Oniscidae) live in 
moist terrestrial localities. Of the some- 
what rare fossil remains, Praearcturus, 
Woodward, is a large form from the Old 
Red Sandstone of Herefordshire ; Amphi- 
peltis paradoxus, Salter, occurs in the Fre. 1408, 
Devonian of Nova Scotia; Arthroplewra, 4° srchaconiscus Brodet, 
Uhlig enirata, Windt, Jordan, is found in the Coal Measures ; ee Bl i 
Lithographic Slates; Urda, Miinster (Fig. 1407), in the Litho- (after Woodward). B, Frag- 
Tene thy ee graphic Slates; Archaeoniscus, M. - Edw. Geendeaiye aoe v1 ne 
(Fig. 1408), in the English Purbeck ; 

Fic. 1407. 
1 Literature : 
Milne-Edwards, H., Sur deux crustacés fossiles (Ann. Sci. Nat. Zool. [2], XX.), 1843.—On 
Archaeoniscus (Ann. Mag. Nat. Hist. [2], XIII.), 1844.—Meyer, H. v., Ueber Palaeoniscus obtusus 
(Palaeontogr., V.), 1858.—Kunth, A., Crustaceen von Solenhofen (Zeitschr. deutsch. geol. Ges., 
XXII.), 1870.— Woodward, H., Several papers on British Fossil Isopods in Trans. Woolhope Field 
Club, 1870; Geol. Mag., VII., 1870; [3], VII., 1890; [4], V., 1898 ; and Quar. Journ. Geol. Soc., 
XXXV., 1879.—Ammon, L. v., Beitrag zur Kenntniss der fossilen Asseln (Sitzungsber. Bayer. Akad. 
Wiss. ), 1882.—Carter, J., On Fossil Isopods (Geol. Mag. [3], VI.), 1889. 

