1922.] vS. Kemp: Notes on Crustacea Decapoda. 139 



Periclimenes beaufortensis Borradaile, Ann. Mag. Nat. Hist. (9) 

 V, p. 132 (1920). 



According to the description this species does not possess 

 exopods on the second and third maxillipeds. It cannot therefore 

 be retained in the genus Periclimenes, but belongs in all probability 

 to Pontonides (see p. 266). 



Periclimenes lenuipes Leach. 



Nobili's statement that Leach described a Mediterranean species 

 under this name is erroneous (v. infra, p. 223). 



Subgenus Periclimenes, sensu stricto. 



The accessory claw or process found on the dactyli of the last 

 three peraeopods in this subgenus is, I presume, to be regarded as a 

 sign of specialization ; Periclimenes s.s. is thus less primitive than 

 Ancylocaris. 



The species included in the subgenus exhibit great variation 

 in habit of body. Some, such as P. longicaudatus are extremely 

 slender in build, while others, such as P. lanipes, are remarkably 

 stout. P. scriptus, the type of the subgenus, is intermediate in 

 form, without any strongly marked characters, and it appears 

 to me probable that it is from some such species as this that the 

 remainder have evolved. 



P. latipollex, P. laccadivensis , P. alcocki and P. lanipes form 

 a rather distinct section of the subgenus, distinguished by the 

 tooth and socket arrangement in the dentition of the fingers of the 

 second leg. P. soror and P. noverca differ from all other species 

 of the subgenus in the possession of a series of fine teeth on the 

 edges of the fingers of the first leg. In this they resemble 

 P. spiniferus, P. petitthouarsi and P. denticulalus,* which belong 

 to the subgenus Ancylocaris. I think it most improbable that 

 there is any real affinity between these two groups of species and 

 regard the similarity in structure of the fingers of the first leg as 

 an instance of convergence. 



Certain species possess characters which are unique in the 

 genus : P. longicaudatus has no antennal spine, P. aesopius has a 

 large compressed tooth on the third abdominal somite and in 

 P. investigatoris the lateral process of the antennule is of abnormal 

 length. 



1 The same character is also found in P.frater. Borradaile considers this 

 species to be a close ally of P. soror, but the dactylus is said to be simple and I have 

 consequently included it in the subgenus Ancylocaris. In P. noverca the accessory 

 claw of the "dactylus is reduced to a mere lobe and it is easy to understand how 

 this lobe might disappear altogether by further modification along the same lines. 

 If Borradaile's views on the relationships of P. fritter are correct, the species has 

 presumably been evolved from one with biunguiculate dactyli and has no affinity 

 with the more primitive forms included in the subgenus Ancylocaris. The 

 position of the species thus requires further consideration. 



