A432 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
Locality. Station VII. E, 2 2 (No. 41 ovig.) [40, 41]. 
Remarks. 2 41 ovig.: C.1. excluding rostral horns 23 mm., rostral horn 1. 
7 mm., eye-stalk 1]. measured from inner orbital angle 6°5 mm., and supra- 
ocular spine 1. measured also from inner orbital angle 7 mm., R= Clb =s30F 
9 40 has C.]. 9 mm., R.1. 3°5 mm., and R.1. + Cl. = °39. 
The following distinctions hold between the present specimens of O. curvi- 
rostris and specimens of O. cervicornis, Herbst, from Ceylon, examined by 
me (Laurie, 1906, p. 383) :— 
1. The rostral horns are distinctly upturned at the tips in curwrostris, not 
in cervicornis. See Rathbun, however, as below. 
2. The rostral horns are closely apposed in curvirostris, 3 te in cervicornis, 
though the rostral horns are somewhat bowed outwards, their tips are well 
apart (e.g. 8 mm. in a specimen with C.1. 45 mm.). 
3. The triangular projection of the posterior border of the carapace is more 
broadly triangular and less elongate in curvirostris. 
4. The form of the external maxillipedes presents two points of difference, 
both in regard to the ischium :— 
(a) the ischium of curvirostris has a deep longitudinal groove on the 
exposed surface, there is in cervicornis only ihe merest trace of such 
a groove. 
(b) in cervicornis the proximal portion of the inner margin of the 
ischium, just before the angle is reached, is strongly notched, so that a 
rounded window is formed when the two ischia are opposed, this window 
is open posteriorly as the proximal angles do not meet in the middle line, 
though each such angle bears a claviform seta and these meet across the 
middle line giving an appearance of completeness to posterior border of 
the window (PI. 45. fig. 5); in curvirostris the proximal angle of the inner 
border of the ischium is cut away and only very obscurely marked, so that 
the regions in question slope obliquely ackwards away from each other 
and the window does not appear, the club-shaped setze are present but are 
far from meeting in the middle line (Pl. 45. fig. 4). 
5. The eye-stalks and the supra-ocular spines are subequal in curvirostris, 
whereas in cervicornis the eye-stalks are quite distinctly the shorter of 
the two. 
Of the above points of difference the first is of doubtful value, Rathbun 
(Rathbun, 1911, p. 254) saying that the rostral horns have their tips recurved 
upward (but not that they are apposed) in a 4 cervicornis from Amirante 
and a young ? from Seychelles which she describes. The condition of the 
ischia of the external maxillipedes may prove, however, to be a distinction of 
considerable importance. 
