2^ CRUSTACEA. 



paulo producto. Articulus antennarum externarum lmus elongatus hiatuin bene 

 occupans. Articulus maxillipedis externi 3tius oblongus, apicc oblique truncatus, 

 in marginis interni emarginatione articulum 4tum gerens. 



(t. 3. Peltarion, Homhron et Jacquinot* — Carapax suborbicularis, ante medium 

 latior, fronte triangulate rostrato. Articulus antennae externa lmus perbrevis, 

 2do parce crassior. Articulus maxillipedis externi 3tius non oblongus, apice 

 truncatus. Articulus pedum 8 posticorum 5tus 4to vix brevior. 



G. 4. Pseudocorystes, Edwards. — Carapax suborbicularis, parce oblongus, trian- 

 gulate rostratus. Articulus maxillipedis externi 3 this vix oblongus. Articulus 

 pedum 8 posticorum 5tus 4to duplo brevior. 



G. 5. Gomeza, Gray.f — Carapax oblongus, fere ellipticus, triangulate rostratus. 

 Oculi parvi vel mediocres. Articulus maxillipedis externi 3tius vix oblongus 

 vel transversus, apice truncatus. Articuli pedum 8 posticorum 4tus et 5tus fere 

 zequi. 



G. 6. Oeidia, Be Haan (parthn).J — Carapax oblongus, antice non angustans, 

 fronte breviter rostrato. Oculi permagni. Articulus maxillipedis externi 3tiua 

 latus, oblongus, 2do paulo brevior. Articuli pedum S posticorum 5tus et 4tus 

 fere asqui. 



G. 7. Corystes, Latrcille. — Carapax oblongus, rostratus. Oeuli mediocres. Ar- 

 ticulus maxillipedis externi 3tius anguste oblongus, 2do vix brevior, 



2. Pedes jposthi natatorli, 



G. 8. Dicera, Be Haan.§ — Carapax oblongus, rostro late triangulato. Pedes 

 postici natatorii, tarso falciformi. Articulus maxillipedis. externi Stius anguste 

 oblongus, 2do parce brevior. 



The areolation of the carapax in the Corystoidca, where distinct, 

 is Cancroid in character, yet with some peculiarities in the more typi- 

 cal species. The medial region is much elongated behind, this elon- 

 gation occurring mainly in the intramedial areolet (3 M), which in its 

 posterior part, is about as long as broad or even oblong, reaching two- 

 thirds of the distance to the posterior margin of the carapax Conse- 

 quently the cardiac areolet is placed far back of the middle in the 

 posterior third of the body. The five teeth or lobes D, E, N, T, S, 

 may be distinctly counted in some species, as in Peltarion and 

 Gomeza (Plate 18), as explained more particularly beyond; and in 

 these and similar cases, the antero-lateral margin extends far back 



* Hombron et Jacquinot, Yoy. au Pole Sud, tab. 8, f. 1. 



f Oeidia, De Haan in part, Faun. Japon., 15. The typical species of Oeidia (#. 20- 

 spinosa) is a true Gomeza, as recognised by Gray. 



J Faun. Japon., 15, 45. Species Oeidia disfincta, Pe Haan, is the typo of the genus 

 as received. Jonas, Hombron et Jacquinut, V<>y. au Pole Sud, tab. 8, f. 4-8. 



§ Faun. Japon., 14 (1833). Nautilocorystvs, Edwards, Crust., ii. 149 (1837). 



