306 MR. E. J. MIERS ON THE PENJEIDiE. [Mar. 5, 



in the British-Museum collection do not enable me to adopt this 

 course, as many species are not as yet represented in it, I have, in 

 the synopsis of the species given below, and until a more complete 

 revision of the genus shall have become possible, included the species 

 in Penceus. 



Synoptic Table of the Species o/Penaeus. 



The object of the following analytical Table is to indicate the prin- 

 cipal external characters by which the species of Penceus may be 

 distinguished. There are certain species which have not been 

 described with sufficient detail to allow of their incorporation in the 

 list ; these are either previously referred to, or are mentioned by Milne- 

 Edwards in the • Histoire Naturelle des Crustaces.' The species of 

 which there are no specimens in the British-Museum collection, and 

 which are therefore unknown to me, are distinguished by an asterisk. 



I. Antennules with both flagella extremely short. Two deep longitudinal 



sulci extending along the whole length of the cephalothorax, adjacent to 

 the rostrum and the median carina, which is itself deeply sulcate. (A 

 supraorbital spine present.) 



First and second pairs of legs bispinose, third pair unispinose at base. 

 Seventh postabdominal segment with lateral marginal spines. 



1. P. caramotc, Eisso. 

 European. 



First pair of legs bispinose, second pair unispinose, third pair unarmed at 

 base. Terminal segment without lateral marginal spines. 



2. P. brasiliensis, Latr. 

 Atlantic region. 



First and second pair of legs unispinose, third pair unarmed at base. Ter- 

 minal segment with lateral marginal spines. 



3. P. canalkulatus, Oliv. 

 Indo-Pacific region. 



II. Antennules longer. No lateral sulci on the cephalothorax, bordering the 



rostrum and median carina. (Supra-orbital spine usually absent.) 



A. Rostrum much longer than the eyes, reaching nearly to, or beyond, the end 



of the antennal scale. 



a. Carapace with a ridge extending backward from the origin of the rostrum 

 to, or nearly to, the posterior margin of the cephalothorax. 



§ The carina between the base of rostrum and posterior margin sulcate, 

 and reaching to the posterior margin. 

 First pair of legs bispinose, second pair unispinose, third pair unarmed at 

 base. Eostrum '-^--dentate, third to sixth postabdominal segments keeled. 



4. P. semisulcatus, De Haan. 

 Japan, Indo-Pacific region. 



First and second pairs of legs unispinose, third pair unarmed at base. 

 Eostrum -^-dentate, curved upward toward the apex; third to sixth post- 

 abdominal segments keeled. 



5. P. hardwickii, Miers. 

 Indian Seas. 



Eostrum ~ dentate, slightly ascending toward the apex. All the postab- 

 dominal segments keeled. 



*6. P. sculptilis, Heller. 

 Java. 



