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Guide to Crustacea. 
Order 2. Decapoda. 
Table- The gills are arranged typically in three series — podobranchiae, 
Nos? 9-16. arthrobranchiae, and plenrobranchiae. Only in the aberrant genus 
Lcucifer are the gills entirely 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. 
Penaeus caramote, from the side, about half natural size. 
[Table-case No. 9.] 
Prawns, and Shrimps. From their greater size and more general 
interest, it is both possible and desirable to exhibit a much larger 
series than in the other groups of Crustacea, and in Table-cases 
Nos. 9 to 16 will be found representatives of all the Tribes and of 
the more important families composing the Order. On the system 
of classification adopted here, these tribes are grouped under three 
Sub-orders : — 
Sub-order 1. — Macrura. 
,, 2.— Anomura. 
,, 3. — Brachyura. 
