10 



The external maxillipeds are pediform and are most often longer than the 

 1st pair of thoracic legs. 



The thoracic legs all consist, usually but not always, of seven movable 

 joints : the first two or three pairs may be chelate, but the last two pairs are 

 never truly so : all 5 pairs are very often slender, but the 1st or the 2nd 

 or the 3rd may be enlarged and massive : though the 4th and 5th pairs 

 may occasionally (Sergestidas) be rudimentary or absent, they are never folded 

 in the branchial chamber. 



The abdominal appendages are particularly well developed, the 1st pair 

 are often biramous. 



The genital openings of the male are almost always in the articular 

 membrane between the sternum and the coxa of the 5th pair of thoracic legs. 



The branchiae are dendrobranchiae or phyllobranchias : only in one small 

 group (Stenopideo) do they resemble trichobranchias. 



Synopsis of the Family-Groups of Macrura Caridides. 



I. The 3rd pair of thoracic legs are chelate : the external maxillipeds are 

 7-jointed : the pleura of the 1st abdominal somite are not overlapped 

 by those of the 2nd : 



1. The 3rd pair of thoracic legs though they may be longer are 



not stouter than the 1st and 2nd pair : the mandibular palp 

 is straight and usually foliaceous : the endopodite of the 

 1st maxillipeds is long : the branchise are dendrobranchire. PENEIDEA. 



2. One or both of the legs of the 3rd pair are not only longer but 



vastly stouter than those of the 1st and 2nd pair : the 

 mandibular palp is stout and incurved : the endopodite of 

 the 1st maxillipeds is short : the branchize resemble 

 trichobranchise ... ... ... ... STENOPIDEA. 



II. The 3rd pair of thoracic legs are monodactylous : the external maxilli- 

 peds are 4- or 5-jointed : the pleura of the 1st abdominal somite are 

 overlapped by those of the 2nd : the brancbice are phylllobranchise... CARIDEA. 



PENEIDEA, Spence Bate. 



Peneens (part) Milne Edwards, Hist. Nat. Crnst. II. 403. 



Peneidea (part) DeHaan, Faun. Japon. Crust, p. 187 and Dana, U. S. Expl. Exp. Crust, pt. I. p. 600. 

 Peneids:, Boas, Vid. Selak. Skr., 6 Raekke, nat. math. Afd. I. 2, 1880, p. 155. 



Peneidea, Spence Bate, Challenger Crust. Macrura, p. 220 : Stebbing, Hist. Crust, p. 313 : Ortmann, in Bronn'g 

 Thier Eeioh, Arthropoda, p. 1117. 



The pleura of the 1st abdominal somite overlap those of the 2nd. 



The incisor portion of the mandibles is separated from the molar portion 

 by a groove : the endopodite (palp) of the mandibles is commonly very large 

 and foliaceous or subfoliaceous. 



