MYSIDEA. Qon 



The third (Sceletinince) , without branchial appendages, and with the 

 inner antennae simple, and the outer two-branched without a proper 

 basal scale. 



The Mysinm have a cavity formed beneath the posterior part of the 

 cephalothorax by plates from the bases of the legs for carrying the 

 eggs before they are fully developed. 



The known genera and subdivisions of the Mysidea, are as fol- 

 lows: 



Fam. I. EUPHAUSIDiE. 



G. 1. Nocticula, Thompson*— Oculi symmetrici, breves. Pedes thoracis qua- 

 tuordecim, duobus posticis obsoletis branchiis exceptis. Flagella duo antennarum 

 internarum elongata. 



G. 2. Euphausia, Dana.— Oculi symmetrici, breves. Pedes thoracis non ungui- 

 culati, numero duodecim, quatuor posticis obsoletis branchiis exceptis. Flagella 

 duo antennarum internarum elongata. Segmentum abdominis posticum acumi- 

 natum. 



G. 3. Cyrtopia, Dana.— Oculi paulo oblongi, apice externo oblique gibbosi, 

 lenticulis totis in gibbositatem versis. Articulus antennarum internarum primus 

 apice inferiore productus. Segmentum abdominis posticum obtusum aut trun- 

 catum. 



Fam. II. MYSIME. 



Subfam. 1. CYNTHIN^].— Pedes abdominis appendicibus branchiali- 

 bus instructi. Antennae internae birameae, externae squama basali 

 instructae. 



G. Cynthia, Thompson.-f— Pedes thoracis quatuordecim, biramei; maxillipedes 

 quatuor. Oculi breves symmetrici. 



Subfam. 2. MYSINiE. — Pedes abdominis appendicibus branchialibus 

 carentes. Antennae internae birameae, externae squama basali 

 instructae. 



* Thysanopoda of M. Edwards. The genus Nocticula of Thompson (Zool. Researches, 

 p. 52, pi. 5, f. 1) is identical either with Thysanopoda or Euphausia, and, as he states 

 the number of pairs of thoracic legs to be eight, it must be identical with the former. 

 The specimens were obtained in the northern Atlantic. 



f Zoological Researches, 55, pi. 6. 



160 



