640 CRUSTACEA. 



nan unguiculati, ciliati, palpo breviore. Branchial multipartitce aut 

 ramosce. Pedes abdominales mediocres, basi oblongo, lamellis ciliatis. 

 Segmentum abdominis posticum elongatum, acuminatum, utrinque 

 barbd nudd prope apicem armatum. 



Eyes short, orbiculate. Inner antennae ending in two flagella, outer 

 having an oblong ciliate scale at base. Thoracic feet six pairs, 

 the two posterior wanting, except the branchias; legs six-jointed, 

 slender, not unguiculate, ciliate, palpus shorter. Branchiae much 

 divided or ramose. Abdominal feet moderately large, consisting of 

 an oblong base and ciliate lamellae. Last segment of abdomen 

 oblong, acuminate, armed on either side near apex with a naked 

 barb. 



Carapax in front with a very short beak. Peduncle of the first 

 antennae long, projecting far beyond the eye, and bearing two long 

 slender flagella, of nearly equal length. Two posterior thoracic legs 

 absent excepting the branchiae, which are larger than the others more 

 anterior. The pairs of branchial appendages seven in number. 



Palpus of mandible three-jointed, inserted near summit ; extremity 

 of mandible with a prominent denticulate edge around the summit. 



The caudal appendages consist each of two oblong plates, nearly 

 equal in length, and but little shorter than the caudal abdominal 

 segment. The inner is slender acuminate and ciliate on both sides. 

 The outer is obtuse at apex and ciliate within. The two setae near 

 apex of last abdominal segment give it nearly a trifurcate appearance, 

 the setae projecting beyond the point between. 



The thoracic legs are usually carried as in the figures, while the 

 palpi or outer branches act as oars in swimming. The legs are fur- 

 nished with long cilias, which are short thin plumose. There are five 

 long slender joints, the last three bent downward ; the next preceding 

 is short and stout, has a transverse position, it bears the palpus near 

 one end, and the continuation of the leg at the other. This transverse 

 joint proceeds from another short joint which bears the branchiae. 



The Euphausicn are brilliantly phosphorescent, and hence the name 

 of the genus ; the phosphorescence proceeds from a part of the cephalo- 

 thorax. 



The species sometimes have a minute red globule near the base of 

 four of the abdominal legs either side, and also two other pairs in the 



