INVEKTEBRATE ANIMALS. 65 



II Examples of Iclotea entomon, from the Baltic, 

 the largest of the Isopods ; Serolis, from the 

 Falkland Islands. 

 Group 165.— Orders L^MODIPODA. Xaifxhi, the throat ; 

 8»?, twice; ttouj, afoot; and AMPHIPODA : ajacfjj, both- 

 ways ; "ttovs, a foot. The species in the former order are 

 few and possess heads indistinctly separated from the 

 thorax ; hence the first pair of limbs seem to be attached 

 to the throat. The order includes the Skeleton-screw, 

 Spectre-shrimp, and the Whale-louse, Cyamus. From 

 the Isopods the Amphipods differ in having pairs of 

 limbs set both-ways, to the front and to the rear. 

 Amongst them are the Sand-hoppers, Talitrus, which 

 occur in millions near the water's edge on sandy coasts, 

 incessantly leaping as if overflowing with the joy of 

 life (Paley). The Coast-screw, Gammarus ; the xylo- 

 phagous Chelura; and the tube-inhabiting Cerapus. 

 Estimated number of species : British, 110. 



Division PODOPHTHALMATA. ttov;, a foot; 

 6<^SaXixo{, an eye. Eyes on footstalks ; body protected 

 by a carapace. 



Group 166.— Order STOMAPODA. (rTo>«, a mouth; ttouj, a 

 foot. Gills external ; pairs of legs, generally seven. The 

 Opossum-shrimps, Mysis, so called from the pouch in 

 which the female carries her eggs, abound in some parts 

 of the Arctic Seas. On the coast of Boothia they form 

 the food of prodigious shoals of salmon : in" the Green- 

 land Seas two species form part of the food of the 

 common whale. Mysis Oheron, found on the coast of 

 Cornwall, is so transparent that in a tumbler of water 

 nothing of it can readily be seen but its pair of black 



