Mr. C. Spence Bate on Synaxes. 227 



IS broad and flat ; and all the legs have the second and third 

 joints fused into one — a feature common to the Palinuridee and 

 Scyllaridse, but not to be found in any other form of the Ma- 

 crura. 



The last or fifth pair of pereiopoda is very much smaller 

 than either of the preceding pairs ; but it terminates in a simple 

 dactylus, whereas in the Scyllaridse and the Palinuridaj, and 

 in some of the genera allied to Pohjcheles, the female has the 

 posterior pair terminating in a minute chela — a feature that is 

 common to the Anomurous Crustacea, but not to be found in 

 the Astacidffi or Homaridge, and separates them from those 

 that possess this character. 



In Synaxes the pleon has a longitudinal central ridge or 

 line of elevation — a feature common to many of the Scyllaridse, 

 but seldom seen in the Palinurid^, although lines of demarca- 

 tion without elevation are apparent in the Palinurus marinus 

 of our seas. It becomes a prominent feature in the Eryonidse, 

 but is never seen in the Astacida or Homaridae. 



The pleopoda are developed very similarly to those which 

 exist in the Scyllaridas, and are distinguishable from those of 

 any other form among the Macrura, especially in the female, 

 where one, the inner (or true representative of the leg), is 

 three-jointed and cylindrical, and the outer is a simple folia- 

 ceous plate. In the Palinuridse in the male there is only the 

 outer leaf-like plate, the inner ramus being absent. In the 

 females the second pair consists of two foliaceous plates, the 

 third and following of one foliaceous plate and a subcylin- 

 drical biramose branch. The appendage which belongs to 

 the anterior somite is well developed in the Scyllaridje, is 

 reduced to a small cylindrical rod in Synaxes^ and is absent 

 in the Palinuridae. 



The position among the Macrura that the present species 

 occupies is very near to Palinurus ; and its departure appears 

 to approximate more or less closely the genera that go to 

 make up the family of the Scyllaridee. The first distinguishing 

 feature is the advanced rostriform projection between the 

 eyes, of which we have no representative in either of the 

 known families, although in some species a small incipient 

 process appears to exist, as in Palinurus marinus. But this 

 feature in Synaxes brings the form of the carapace into close 

 resemblance with that of the Astacidea, from which it may be 

 distinguished by its being secured at the posterior margin. The 

 breadth of the ventral surface of the pereion, the form of the 

 pereiopoda and antennae are all peculiar to the Palinuridse, 

 whereas those of the pereiopoda and the pleopoda are essen- 

 tially features of the Scyllaridse. It would thus appear that the 



17* 



