REPORT ON THE CRUSTACEA MACRURA. 505 



the intended blow miss its mark, the several dorsal processes in the median line 

 become structurally protective, for the telson when fixed for striking, is supported in 

 position by the tubercle on the dorsal surface being brought into contact with the 

 posterior tooth of the sixth somite, and in the same way support is given by several 

 successive somites until the first is relieved by the pressure of the antero-central tooth 

 against the postero-dorsal surface of the carapace. 



The ophthalmopoda are short and support large and globular ophthalmi. On the 

 inner surface near the ophthalmus in some species a small denticular projection is present 

 that I take to be the representative of a phosphorescent organ. The ophthalmopoda 

 rest in an orbit which is defined by a large projecting tooth on the outer canthus. 



The first pair of antennae is short and terminates in two short flagella ; the basal joint 

 is hollowed to receive the eye when at rest, and is without a stylocerite. 



The second pair of antennas carries a scaphocerite that is broad and discdike, 

 the outer margin being as soft and flexible as the inner ; it is fringed with fine 

 hairs. The tooth commonly present on the outer margin of this organ is wanting or 

 reduced to a minute denticle, easier felt than seen, and is situated about one-third the 

 length of the organ from the base. This antenna carries a flagellum that nearly equals 

 half the length of the animal. 



The mandibles are similar to those in the genus Crangon, they carry no psalistoma 

 or synaphipod, and are enclosed within the lips. 



The first pair of siagnopoda are small, three-branched, and closely hug the oral walls 

 on each side. The second pair of siagnopoda consists of two branches ; the inner, or 

 that nearest the mouth, is small, tapering and two-jointed, the outer is broad and 

 subfoliaceous, and represents the mastigobranchial plate ; it is uniarticulate (and there- 

 fore not correctly represented on PL XCII.,/), the anterior extremity being rounded and 

 fringed with hairs, as is the posterior extremity, which projects beyond the articulation, 

 the margin being fringed with hairs centrifugally directed, their extremities being curved 

 towards the anterior end. 



The third pair of siagnopoda is four-branched, the inner branch is small and 

 rudimentary, the second is flat, pointed, and fringed with hairs ; the third is broad, 

 rounded at the extremity, fringed with hairs, and from the inner margin a slender lash-like 

 process projects anteriorly ; the fourth represents the mastigobranchial appendage, and 

 consists of a long, narrow, hairless plate directed both anteriorly and posteriorly. 



The first pair of gnathopoda is seven -jointed ; the second joint or basis carries a long, 

 gradually tapering, lash-like basecphysis fringed with small hairs ; the ischium and 

 meros are broad at the base but become narrow towards the distal extremity ; the carpos 

 is short and suddenly enlarges, the broader extremity supporting the propodos, which is 

 long, flat, and distally obliquely truncate, the margin bearing a wide and short dactylos. 



The second pair of gnathopoda is only five-jointed. The first two joints, the coxa 



(ZOOL. CHALL. EXP. — PAET. LII. — 1887.) Fff 64 



