BORRADAILE— ON THE PONTONIIN^ 361 



with short wrist, and unarmed, save that in P. gracilis the angles of the wri^t and arm 

 are sharp. 



Key to the species of Peridimenes (Cristiger) : 



I. Rostrum much shorter than antennular stalk. Second leg shorter than first. 

 [R. =|-, lanceolate, two teeth behind orbit.] 



P. (C) brevinaris Nobili, 1905. 



II. Rostrum little if at all shorter than antennular stalk. Second leg longer 

 than first. 



A. Three or four rostral teeth behind orbit. Three teeth below rostrum. 



Atlantic and Mediterranean. 



1. Rostrum deep, horizontal. Second leg outreaches antennal scale by hand 



only. European. [R. = ^.] 



P. (C.) scriptus (Risso), 1826. 



2. Rostrum shallow, bent downwards. Second leg outreaches antennal scale 



by wrist and hand. W. Atlantic. [R. =§.] 

 P. (C.) tenellus (Smith), 1882. 



B. No rostral tooth behind orbit. Very rarely more than one tooth below 



rostrum^'. Indopacific. 



1. Rostrum lanceolate. 



a. Dorsal edge of rostrum bears nine or more teeth. 



i. Antepenultimate joint of third maxilliped broad. R. =^^^. Fingers 

 of first leg not denticulate. 



P. (C.) hrochi (de Man), 1887.. 



ii. Antepenultimate joint of third maxilliped narrow. R. = ii-i3 . 

 Fingers of first leg denticulate. 

 a. First joint of antennule bears two distal spines. No accessory 

 ' spinule on dactylopodites of last three legs. 

 P. (C.) frater Borradaile, 1915. 



fi. First joint of antennule bears one distal spine. An accessory 

 spinule on dactylopodites of last three legs. 

 P. (C.) soror Nobili, 1904. 



h. Dorsal edge of rostrum bears seven or fewer teeth. 



i. Ventral edge of rostrum bears more than one tooth. 



a. A supraorbital spine. [R. = |-.] 



P. (C.) commensalis Borradaile, 1915. 



* Only F. notatus has three, 

 SECOND SERIES— ZOOLOGY, VOL. XVIL 46 



