CRUSTACEA. 663 
Leucifer THompson, Epw. Head narrow, produced into a pe- 
duncle sustaining the antenne and petiolate eyes, longer than the 
thoracic shield. Abdomen slender, elongate, with segments oblong. 
(Branchie unknown.) 
Compare Epwarps Hist. nat. des Crust. 1. pp. 467—469, Plate 26, 
fig. 10. Habit, excepting the head, nearly that of Alima. 
Thysanopus (Thysanopoda Epw.). Shell anteriorly acuminate, or 
supplied with a rostrum. Maxilliform feet none. Eight pairs of 
feet of trunk; first seven slender, supplied with a cirrus or long 
external oar. Branchiew ramose, fasciculate, adhering to the base 
of thoracic feet, free. First five pairs of abdominal feet bifid, 
natatory. 
Sp. Thysanopus tricuspidatus MitnE Epwarps, Ann. des Sc. nat. Tom. XIX. 
1830, pp. 451—460, Pl. 19, Hist. nat. des Crust. Pl, 26, fig. 1. 
Cynthia THOMPSON. 
Mysis Larr. Shell with rostrum none or very short anteriorly, 
deeply emarginate posteriorly. Antenne 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. Branchiz none distinct. 
Sp. Mysis flecuosa, Cancer flecuosus MUELL., Zool. danic. Tab. 66, figs. I—9, 
Hersst Arabben, Tab. 34, figs. 8,9, RaTHKE Beitr. zur Fauna Norwegens, 
pp. 18—20.—Mysis oculata, Cancer oculatus O. F. Fasricit Fauna Grenl. 
pp. 245, fig. 1 (copied in HEerzst Tab. 34, figs. 5, 6), &c. The size of the 
species of this genus varies from 6’’—1”"; 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. Frey u, LEvcKART, 
Beitrige zm Kenntniss wirbelloser Thiere. Braunschweig, 1847, 4to, 8. 
ILIO—130. 
Family of uncertain position. Cuwmacea KROEYER. 
Cuma Epw. 
Compare Epwarps Ann. des Sc. nat. XiI. 1828, pp. 294—2096. 
Epwarpbs, at a later period (Hist. nat. des Crust, U1. p. 553) announced 
the opinion that this genus has no foundation, and that the little animal 
