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



Acanthephyra, A. Milne-Edwards. 



Acanthephyra, A. Milne-Edwards, Arm. d. Sei. Nat., ser. 6, tom. xi. p. 12, 1881. 



,, Sidney Smith, Dec. Crust. Albatross Dredgings, 1883 — in Eep. Commiss. 



Fish and Fisheries, p. 372, 1884. 

 Non Miersia, Kingsley, Proe. Acad. Nat. Sci. Philad., p. 416, 1879. 



„ Sidney Smith, Bull. Mus. Conip. Zool., vol. x. p. 66, 1882. 



Body laterally compressed and dorsally arcuate from crest to telson. Carapace 

 smooth, compressed anteriorly to a greater or less carina, and produced to a long and 

 slender rostrum that is furnished with a larger or smaller number of teeth on the upper 

 and lower margins ; frontal margin depressed and excavated to form an orbit, the outer 

 can thus being defined by a rounded angle, external to which stands the first antennal 

 tooth, then a second excavation is formed to receive the second pair of antennae, at the 

 lower angle of which the second antennal tooth projects, and beyond this the frontal 

 margin of the carapace recedes obliquely backwards and inwards for a short distance, and 

 is then continued still more abruptly inwards as the lateral margin, making a distinct 

 angle with the branchial walls of the carapace, recedes from the frontal to the posterior 

 margin. 



The first somite of the pleon is as deep as the carapace, the posterior surface of which 

 it laterally overlaps. The second and following somites are carinated, the four posterior 

 being generally produced posteriorly in the form of laterally compressed teeth, which, 

 when the animal is fully extended, lie against the dorsal surface and form a cultriform 

 carina. 



The telson is long, slender, and tapering. 



The ophthalmopoda are short, oblong, and carry a small and imperfect ocellus. 



The first pair of antennae has the peduncle short ; the first joint is excavate on the 

 upper surface and carries a stout stylocerite ; the second and third joints are cylindrical, 

 and terminate in two long flagella. 



The second pair of antennae is long and slender, and carries a long and sharp-pointed 

 scaphocerite, that articulates between two strong teeth. 



The mandibles are deeply placed within the oral cavity ; they have the psalistoma 

 strongly serrate, concave, and continuous with the molar process, and carry a two- 

 jointed synaphipod. 



The first pair of gnathopoda is subpediform, seven-jointed, and has the distal joints 

 enlarged and reflexed ; the basis carries a long ecphysis, and the coxa supports a short 

 mastigobranchial plate, to which is attached a small podobranchial plume and another is 

 attached to the membranous articulation. 



The second pair of gnathopoda is long, straight, pediform, and five-jointed ; the 

 three terminal joints are long, the distal one ends in a sharp styliform point ; the basis is 



