REPORT ON THE CRUSTACEA MACRURA. 701 



and is interlocked and articulates with the anterior margin of the first somite of the 

 pleon. 



The third and following somites of the pleon are posteriorly produced in the median 

 line to long teeth, that correspond in form with the dorsal surface of the animal, so that 

 when it is extended they rest upon the back in the form of a strong carina. 



The telson terminates in a sharp point. 



In some species there is also a tooth at the inferior margin of the coxal plate of the 

 first somite of the pleon, which acts as a buffer against which the projecting tooth of the 

 posterior angle of the carapace strikes when the animal rolls itself up. 



The frontal surface of the margin near the orbit turns inwards and forms a sulcus, 

 posteriorly narrowing to the hepatic region ; anteriorly the outer canthus of the orbit 

 appears to be lost or is coincident with the first antennal tooth, which is directed 

 inwards and downwards and meets a small process attached to the upper surface of the 

 peduncle of the second pair of antennae, and so acts that when the scaphocerite is 

 extended laterally it resists its return. The tooth that corresponds with the second 

 pair of antennas also assists in supporting the scaphocerite in an extended position. 

 From the second antennal tooth to the frontodateral angle the margin descends vertically 

 and is produced to a strong tooth that is directed outwards and forwards, the margin 

 then turns abruptly inwards at right angles, and so continues along the lateral margin 

 to a largely developed tooth at the posterior angle of the carapace. Near the middle of 

 the lower border of the carapace there is a depression, not in the margin itself, but in 

 the angle produced by a bent longitudinal curvature of it. 



The ophthalmopoda are short and carry a large ophthalmus that has a circular 

 ocellus closely impacted in its margin ; on each side a small tubercle projects into the 

 ophthalmus, and on the inner side, distant from the others, there is a small tubercle. 



The first pair of antennas has a short peduncle and carries two long flagella. 



The second pair carries a long, strong scaphocerite, that tapers to a sharp point and 

 is capable of being rigidly locked in position and unfixed at will, and a long and slender 

 flagellum. 



The mandibles have the psalistoma connected with a small molar process and support 

 a synaphipod of three joints. 



The first pair of gnathopoda is subpediform, and has the terminal joints reflexed. 



The second pair is five-jointed ; the ischio-meral joint is flattened, strongly curved, 

 and the basis carries a long and flat ecphysis. 



The first two pairs of pereiopoda are short, subequal, robust, and chelate, having the 

 carpos short and uniarticulate. The following three pairs are short and terminate in a 

 styblform dactylos, of which that of the posterior pair is somewhat the shortest ; 

 all carry a straight and rather broad basecphysis, and attached to the coxa of each, 

 except the posterior pair, is a small mastigobranchia that passes between the branchige. 



(ZOOL. CHALL. EXP. PART LIL 1887.) Fff 96 



