170 THE VOYAGE OF H.M.S. CHALLENGER. 



me to determine that the brephalos when it first leaves the ovum, is in the Megalopa 

 stage, as shown in PI. XX. fig. 2. The ophthalmopoda are clearly defined as well- 

 developed lobes of conspicuous proportions, as are the two pairs of antenna?. 



The mandibles are less conspicuous but distinguishable, and the pereiopoda are visible 

 in their position on each side of the folded caudal extremity, which terminates in two 

 rounded lobes, one on each side of a central excavation. 



The ovum is about 1'5 mm. in diameter, and perfectly spherical, and not at all 

 suggestive of Ampkion, which genus Boas l thinks may probably be the young of 

 Willemcesia. 



Family Homaeidj. 



Cephalon subcylindrical. Carapace anteriorly rostrated, posteriorly produced over 

 the anterior half of the first somite, but not kept down by a pleocleis. 



Pleon with somites dorsally overlapping each other. 



Pereiopoda seven-jointed, anterior three pairs chelate, first pair largest. Rhipidura 

 well-developed, outer ramus having a diaeresis. 



Mastigobranchise large, having a well-developed podobranchial plume attached to 

 all the pereiopoda except the posterior pair. 



This family consists of the following genera : — Phoberus, Nephropsis, Nephrops, 

 Honmrus. 



Phoberus, A. Milne-Edwards. 

 Phoberus, A. Milne-Edwards, Ann. d. Sci. Nat. (Zool.), sir. 6, vol. ii. p. 15, 1881. 



Carapace slightly compressed laterally, armed anteriorly with a long and narrow 

 rostrum furnished with lateral teeth. Pleon laterally compressed, coxal plates deep. 

 Rhipidura large and well-developed, outer ramus of the posterior pair of pleopoda having 

 a well-marked diaeresis. Telson quadrate, terminal angles slightly rounded off. Eyes 

 small, close together, implanted on short rudimentary ophthalmopoda. First pair of 

 antennae short, supporting two long and slender subequal flagella. Second pail 1 of 

 antennas supporting a large and well-developed scaphocerite, of which the outer margin 

 is produced to an acute point. 



First pair of pereiopoda long, slender, and chelate ; second and third pairs also chelate, 

 but slightly shorter and much more slender ; fourth pair simple, styliform ; the fifth not 

 chelate, but a polliciform process is produced at the inner distal angle of the propodos. 



Geographical Distribution. — The specimens in the Challenger collections were taken 

 in the Papuan Seas. Others closely allied have been taken by Alexander Agassiz in 

 the West Indies. 



1 Zool. Anzeiger, ii. pp. 25U-258. 



