304 Transactions. — Zoology. 



those which possess the stridulating organ. A second very natural sub- 

 division, but of less importance than the first, is indicated by the line c d 

 which divides the stridulating species into brevicorn and longicorn forms. 



For systematic purposes it will probably be convenient to employ both 

 these boundary lines, that is, to divide the species into three sub-genera 

 instead of two as heretofore. The non-stridulating species or Silentes form 

 the first sub-genus, which I propose to call Jasus : * the stridulating forms 

 or Stridentes fall into two sub-genera, one of brevicorn species, to which the 

 name Palinurus may be restricted, and one of longicorn species, equivalent 

 to Milne-Edwards's Langovstes longicornes, Gray's Panulirus, and Pfeiffer's 

 Senex. 



Put in a tabular form the classification I propose is as folloAvs : — 

 Genus Palinurus, Fabr. 



A. Silentes. Stridulating organ absent ; rostrum well developed, clasped 



by paired pedate processes of the epimeral plates ; procephalic pro- 

 cesses present; coxocerites imperfectly fused ; antennulary flagella 

 short. 



Sub-genus Jasus, T.J. P., 

 Includes P. lalandii, P. edwardsii, and P. hiigelii. 



B. Stridentes. Stridulating organ present; rostrum variable, but rarely 



(? never) as well developed as in A ; pedate clasping processes 

 absent ; procephalic processes absent. 



a. Antennulary sternum narrow below and bases of antenna? con- 



sequently approximated ; bases of antennules hidden, in a 

 view from above, partly by the antennulary sternum, partly 

 by the antenna? ; coxocerites imperfectly fused ; antennulary 

 flagella short. 



Sub-genus Palinurus, Fabr., in part. 

 a. Eostrum well developed, covering ophthalmic segment. 



P. trigonus. 

 /3. Eostrum reduced to a small spiniform tubercle ; oph- 

 thalmic segment uncovered. 

 P. vulgaris. 



b. Antennulary sternum broad below, causing a wide separation 



of bases of antenna? ; bases of antennules visible in a view 

 from above ; rostrum absent ; ophthalmic segment uncovered ; 

 coxocerites perfectly fused ; antennulary flagella long. 

 Sub-genus Panulirus, Grey, Senex, Pfeiffer, 

 Includes P. interrnptus, P. japonicus, P. penicillatus, P. ornatus, etc. 



* Jasus, according to Lernpriere, was the father of Palinurus. 



