MACRURA. SCHMITT. 359 



Genus PENEUS, Weber, Alcock. 



Key to the Species of Pene/us (s.s. ) known 



from Australia and the Indo-Paciftc. 



I. Lateral grooves on the carapace extending practically the 

 entire length of the carapace, rostrum with only one tooth 

 on inferior margin. 



A. Telson with three pairs of lateral spines. 



1. Lateral grooves on carapace paralleling medially 

 sulcate post-rostral carina to posterior margin of 

 carapace. 



a. Rostrum without a secondary or accessory pair of 

 lateral rostral sulci. 



i. Thelycum tubular (oval in cross-section), the 

 two lateral plates being indistinguishably united 

 on the median line to form a single large plate. 

 Petasma with submedian teeth or "horns" bent 

 over, so as to overhang the distal margin of the 

 side plates of the petasma. 



japonicus. Bate. 



ii. Thelycum composed of two distinct plates, juxta- 

 posed, but not united on the median line. Petasma 

 with submedian teeth or protuberances but 

 slightly bent over, and not overhanging the distal 

 margin of the side plates of the petasma. 



latisulcatus, Kishinouye (p. 365). 



b. Rostrum with a secondary pair of lateral carinse sub- 

 tending an accessory pair of lateral sulci on the 

 sides of the upper blade of the rostrum, not extend- 

 ing backward behind the last rostral (gastric) tooth. 

 Thelycum and petasma much as in P. latisulcatus. 



jrtebejus, Hess (p. 367). 



2. Lateral grooves on carapace posteriorly confluent, 

 uniting behind the sulcated post-rostral carina and 

 crossing over to form an X-shaped depression. 



maccullochi, new species (p. 370), 

 B. Telson laterally unarmed. 



canaliculatus (Olivier). 



II. Lateral grooves on the carapace not extending posterior to 

 the last rostral (gastric) tooth; rostrum with two to five 

 teeth on inferior margin. Telson laterally unarmed. 



A. Carapace with a more or less prominent subhepatic crest. 



1. No exopodites on the fifth pair of legs; subhepatic 

 crest a prominent longitudinal ridge extending 

 posteriorly for about one-third its length behind the 

 angle formed below the hepatic spine by the meeting 

 of the antennal sulcus with the ridge which terminates 

 anteriorly in the antennal spine. Post-rostral carina 

 usually more or less sulcate. 



carinatus, Dana. 



2. Fifth pair of legs with small but well-formed exopodites. 

 a. Post-rostral carina sulcate; subhepatic crest formed 



by the lower margin of an oblique "incision" 



