CRUSTACEA. 663 



Leucifer THOMPSON, EDW. Head narrow, produced into a pe- 

 duncle sustaining the antennae and petiolate eyes, longer than the 

 thoracic shield. Abdomen slender, elongate, with segments oblong. 

 (Branchiae unknown.) 



Compare EDWARDS Hist. nat. des Crust. II. pp. 467 469, Plate 26, 

 fig. 10. Habit, excepting the head, nearly that of Alima. 



Thysanopus ( Thysanopoda EDW.) . Shell anteriorly acuminate, or 

 ipplied with a rostrum. Maxilliform feet none. Eight pairs of 

 it of trunk; first seven slender, supplied with a cirrus or long 

 external oar. Branchiae ramose, fasciculate, adhering to the base 

 of thoracic feet, free. First five pairs of abdominal feet bifid, 

 natatory. 



Sp. Thysanopus tricuspidatus MILNE EDWABDS, Ann. des Sc. nat. Tom. xix. 

 1830, pp. 451 460, PI. 19, Hist. nat. des Crust. PI. 26, fig. i. 



Cynthia THOMPSON. 



Mysis LATE. Shell with rostrum none or very short anteriorly, 

 deeply emarginate posteriorly. Antennae long, external, with a 

 basal lamellose appendage. Two pairs of maxilliform feet. Six 

 pairs of feet of trunk natatory, furnished with a long external 

 articulate cirrus. Branchiae none distinct. 



Sp. Mysis flexuosa, Cancer flexuosus MUELL., Zool. danic. Tab. 66, figs, i 9, 

 HERBST Krabben, Tab. 34, figs. 8, 9, KATHKE Beitr. zur Fauna Norwegens, 

 pp. 18 20. Mysis oculata, Cancer oculatus 0. F. FABRICII Fauna Grcenl. 

 pp. 245, fig. i (copied in HERBST Tab. 34, figs. 5, 6), &c. The size of the 

 species of this genus varies from 6'" i" ; their synonymy is still very 

 uncertain and confused. 



The thin dorsal shield or the shell probably serves for respiration, as in 

 Apus. Compare on the structure of this genus H. FRET u. LEUCKART, 

 Beitr age zur Kenntniss wirbettoser Tkiere. Braunschweig, 1847, 4to, s. 

 no 130. 



Family of uncertain position. Cumacea KROEYER. 



Cuma EDW. 



Compare EDWARDS Ann. des Sc. nat. xin. 1828, pp. 294 296. 

 EDWARDS, at a later period (Hist. nat. des Crust, in. p. 553) announced 

 the opinion that this genus has no foundation, and that the little animal 



