50 



Guide to Crustacea. 



Order 2."Decapoda. 



Tabl 



cases 



The gills are arranged typically in three series — podobranchiao, 

 Nor<j IG arthrobranchiae, and pleuroliranchiae. Only in the aberrant genus 

 Lcncifcr are the gills entirel}- absent. The first three pairs of 

 thoracic limbs are more or less completely modified to act as jaws 

 (maxillipeds), while the last five form the legs. 



This very extensive and varied Order includes all the larger 

 and more familiar Crustacea, such as Crabs, Lobsters, Crayfish, 



Fig. 31. 



Pciiaeufi caramotc, from tlie side, aliont half natural size. 

 [Table-case No. [).] 



Prawns, and Shrimps. From their greater size and more general 

 interest, it is both possible and desirable to exhibit a much larger 

 series tlian in the other groups of Crustacea, and in Talile-cases 

 Nos. 9 to 16 will be found representatives of all tlie Tribes and of 

 the more important families composing the Order. On the system 

 of classification adopted liere, these tribes areVrouped under tlu-ee 

 Sul)-orders : — 



Sub-ordor 1. Macrui'a. 

 ,, 2. — .Vnoiiuii'a. 



3. — ] )i'acli\ura. 



