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Anomala than to the Crabs ; yet I am convinced that the Anomala, as denned 

 by DeHaan, are a very natural— though they certainly cannot be a " monophyletic " 

 group ; and I think it is convenient to recognize them as a primary division 

 of the Decapod Crustacea. 



The Anomala may be recognized by the following characters :— 

 The abdomen in its entirety is less well developed than the cephalothorax : 

 though m a few exceptional forms it is elongate and extended in a straight line, 

 it is as a rule flexed on itself, or flexed against the thoracic sternum, or is coiled 

 in a spiral, in which last case it is more or less soft and asymmetrical. 



The carapace is traversed on either side, in a longitudinal or obliquely-longi- 

 tudinal direction, by a distinct suture— the linea anomurica— which marks off 

 more or less of the sidewall of the carapace from the dorsal and dorso-lateral 

 region. 



The last thoracic somite is independent, the last thoracic sternum, when it 

 is not atrophied, being separate and freely movable. 



In correspondence with the reduction of the last thoracic somite, the last 

 pair of thoracic legs are always reduced in length. 



The 1st pair of legs are well developed and chelate, the 2nd and 3rd pairs 

 are well developed and monodactylous ; either the 4th and 5th pairs are both 

 much reduced in size, or if the 4th pair are as well developed as the 2nd and 3rd 

 then the 5th pair are slender, weak, and folded. 



The genital ducts never open upon the sternum. 



In addition, the following points are characteristic of the suborder, though 

 they are not constant :— 



The rostrum is often ill-developed and often fails to cover the ophthalmic 

 somite completely. 



The abdominal pleura when present (as often they are not) are almost never 

 bent at a strong angle with their terga, but are extended laterally in the same 

 plane with them. 



There may sometimes be an orbital notch, but the eyes are never concealed 

 in orbits. 



The antennular peduncle is generally weak and flexed and longer than the 

 flagella. 



The antennal scale, when present, is an " acicle," and is never foliaceous. 



The external maxillipeds are commonly pediform. 



Bpipodites are very much more often absent than present on the thoracic 

 legs and 2nd maxillipeds. 



The abdominal appendages are weak, and have a tendency to become 

 rudimentary or to disappear on one or both sides. 



