REPORT ON THE CUMACEA. 



33 



The family at jjresent comprises three genera, viz., Leucon, Kroyer, Eudorella, 

 Norman, and Eudorellopsis, G. 0. Sars, the two first of which are represented in the 

 Challeuger collection. These two genera are easily recognised by the structure of the 

 carapace, as follows : — 



Carapace 



compressed, with a dorsal serrate crest; pseudorostral projection prominent, 

 antero-lateral corners of carapace more or less produced, .... 



very short, truncated in front, dorsal surface smooth, pseudorostral projection 



Leucon, Kroyer. 



Eudorella, Norman. 



Genus 1. Leucon, Kroyer, 1846. 

 Leucon, Kroyer, Nat. Hist. Tidsskr., Bd. ii. Heft. ii. p. 208. 



Generic Characters. — Body very slender. Carapace compressed, with a dorsal serrate 

 crest (sometimes obsolete in male) ; pseudorostral projection prominent ; antero-lateral 

 angles of carapace more or less produced. Antennula? of usual structure, not geniculate, 

 inner flagellum mostly rudimentary ; antenna? in female triarticulate, in male attaining the 

 length of the body. First pair of legs elongate, gradually tapering, clothed with ciliated 

 bristles; terminal joint compressed and armed at the tip with curved spines; second 

 pair rather powerful, ischial joint obsolete, terminal more or less compressed and armed 

 with stiff radiating spines. Last caudal segment slightly produced at the end. Uropoda 

 rather powerful, scape cylindrical, both branches biarticulate, inner spinose, outer 

 setose. 



Remarks. — This genus is chiefly distinguished by the form of the carapace, which 

 exhibits a well-marked dorsal crest, more or less strongly denticulate, and a distinctly 

 prominent, often very elongate, pseudorostral projection. In anatomical details it 

 exhibits great affinity to the genus Eudorella, except that the antennulas are less 

 powerful in structure, and not, as in that genus, geniculate. The genus at present 

 comprises, besides the two new forms described below, nine species, seven of which are 

 from the Northern Ocean, one from the Mediterranean, and one from the Atlantic. The 

 two species procured during the Challenger Expedition are easily distinguished by the 

 following characters : — 



Pseudorostral 

 projection 



triangular, comparatively short, scarcely longer than frontal lobe. 

 Dorsal crest of carapace densely serrate. Inner branch of 

 uropoda shorter than outer, ....... 



conical, very slender and elongate, slightly ascending. Dorsal 

 crest of carapace with scattered denticles. Inner branch of 

 uropoda longer than outer, ....... 



Leucon assimilis, n. sp. 



Leucon tenuirodris, n. sp. 



(ZOOL. CHALL. EXP. — PART LV. — 1887.) 



Iii 5 



