364 "ENDEAVOUR" SCIENTIFIC RESULTS. 



this convexity above the orbit, the upper blade of the 

 rostrum of P. carinatus is quite narrow, only about half 

 the width of that of specimens of P. esculent us of the 

 same size; (3) also in specimens of the same size, the 

 carapace of P. esculentus is shorter and much stouter 

 than in P. carinatus; (4) the cervical groove of P. 

 cat hiatus is quite short (much as in Alcock's figure), 

 being often more or less obscure, or even obsolescent 

 at times; likewise the antenna! sulcus is very short 

 anteriorly,, both of these grooves being only a third as 

 long, relatively, as they are in P. esculentus', (5) a further 

 difference between the two species is to be found in the 

 prominence, position and length of the subhepatic crest 

 or ridge; in fact all the species of Peneus having sub- 

 hepatic ridges, three or more teeth on the lower border 

 of the rostrum and no lateral spinules on the telson, 

 differ with respect to this character: (a) in P. esculentus 

 it is more the slightly turned-up or bent outward lower 

 margin of a straight, longitudinal incision which extends 

 posteriorly scarcely as far as the angle formed by the 

 meeting of the antenna! sulcus with the ridge which 

 terminates anteriorly in the antennal spine, situated 

 below the hepatic spine; (b) in P. carinatus it is a 

 strongly raised, prominent, longitudinal ridge extending 

 posteriorly for about one-third its length behind the 

 angle corresponding to the one defined above; (c) in 

 P. semisulcatus (de Man, loc. cit., 1911, p. 99) the crest 

 is formed much in the same manner as that in P. esculen- 

 /K.V, or, as de Man states: "The subhepatic 'crest' appears 

 as a narrow, linear groove and hardly may be described 

 as a crest," but in contrast to the subhepatic crest in 

 P. esculentus it is oblique, and at an angle of nearly 

 30 degrees to the longitudinal axis of the carapace, 

 beginning behind and a little above the antennal sulcus- 

 ridge angle, below the hepatic spine, and running down- 

 ward toward the antero-lateral angle of the carapace. 



The petasma in the male is anteriorly (distally) 

 much as in P. latisulcatus, but posteriorly (proximally) 

 has no lobes forming a bifurcation below, being evenly 

 rounded on each side of a median notch. 



The thelycum of P. esculentus has the medial 

 margins of the lateral plates very prominent, raised as 

 high as half the width of the remaining portion of either 

 lateral plate. These raised margins are juxtaposed and 



