M Y S I D E A. 651 



totis palpo natatorio extus instmctis. Pedes abdominis natatorii, sub- 

 cequi. \_Segmentum abdominis in specie scrutatd posticum emarginatum 

 vel bilobatumJ] 



Near Mysis. First antennje having two flagella and an oblong scale 

 at apex of base. Eyes symmetrical, short. Thoracic feet twelve, 

 tarsus not jointed, unguiculate ; four pedi form maxillipeds; second 

 pair of maxillipeds and all the feet with a natatory palpus. Abdo- 

 minal feet natatory, subequal. [Last segment of abdomen in the 

 known species emargiuate or bilobate behind.] 



This genus is closely allied to Mysis, from which it differs in not 

 having the tarsus many-jointed. The abdominal feet are all well deve- 

 loped and natatory. The first antennge have an oblong lamella at 

 apex of basal portion, as well as two long multiarticulate flagella; one 

 of the flagella (the upper) commonly is slightly stouter at base, and 

 hairy in this part on one side. 



Seven pairs of pediform organs have similar natatory palpi : but 

 the first of these pairs is shorter than the following, and is thrown 

 forward with the extremity downward, while the others are flexed 

 outward and forward ; it is, therefore, properly a pair of maxillipeds. 

 Anterior to these organs, there is another pair of maxillipeds slightly 

 stouter than the second pair, and having a similar position. 



The inner caudal lamella) have a small, transparent, globular gland 

 in the basal portion, like Mysis. 



PROMTSIS ORIENTALIS. 



Carapnx breviter rostrahis, rostro oc.ul.is multo breviore. Antennce in- 

 ternee apice basis valde crassce, articulo tertio vix oblonyo, Pedes 

 thoracis gracillimi, breviter et sparsim ciliati, ungue oblongo, lenuissimo, 

 palpo multo breviore quam ramus pedifonnis. Segmentum abdominis 

 posticum supra- longitudinaliter concavum, lamellis caudalibvs valde 

 brevins, basi latins et crassius, apice paulo farcatum et acutum, mar- 

 ginibus breviter spinulosis. Lamella caudalis externa internd multo 

 loujior, extus intusque ciliata. 



Carapax short beaked, beak much shorter than the eyes. Interior an- 



