73 
2, may be the same as P. monodon. Desmarest in 1825 men- 
tions the name, but, as Bate has pointed out, no doubt mis- 
apprehended the species. Krauss reports it from the coast of 
Natal. He states that his largest specimens from frontal 
margin to apex of telson were only three inches five lines long ; 
the rostrum somewhat longer than the peduncle of the first 
antennae, with seven teeth above and three below, the hind- 
most of the upper teeth being situate in the middle of the 
carapace ; the colour yellowish-green with cross stripes. Miers, 
Bate, and de Man agree in thinking that P. semsulcatus is the 
same species as P. monodon, although the last-named writer 
still in 1892 retains de Haan’s name for the species (Opy cit, 
p. 510) in the very work in which he decides that Fabricius has 
the priority. According to de Haan, as Bate notices, the 
internal flagellum of the first antennae is twice as long as the 
external. But the figure which de Haan gives in no way 
supports his statement, since it shows the lower flagellum only 
a very little longer than the upper one. This is in accord with 
de Man’s statement (op. cit., 1888) that “the flagella of the 
internal antennae have both nearly the same length, being a 
little longer than the peduncle, 7.e., the distance from the 
distal end of the terminal joint of the peduncle to the anterior 
margin of the carapace.”” He adds that “ the upper or external 
flagellum is a little broad and grooved along the proximal third 
of its length; whereas the remaining part, like the other 
flagellum, is cylindrical.” Dana says of his P. carinatus, 
“flagella of inner antennae not longer than two preceding 
joints,” but as he omits these antennae altogether from his 
figure of the carapace, we cannot be very sure that he knew 
much about them. 
The only mark by which de Haan distinguished his species 
from P. monodon is that in the latter there is no furrow between 
the base of the rostrum and the hind margin of the carapace, 
whereas in P. semisulcatus there is such a furrow. Upon which 
Bate observes that of (two) specimens, “* taken in the same haul, 
the female has a median groove, but in the male there is none, 
the dorsal carina being entire.” In a male eight inches long, 
and a female seven inches long, both sent me from Borneo by 
Dr. Charles Hose, behind the hindmost tooth on the carapace 
the carina is sulcate, but more firmly in the female than in the 
male. On the other hand, in a female seven and a half inches 
long, from the Durban Museum, and in a female seven inches 
long from “ near Port Elizabeth, Zwartskop River,” the carina 
has a flat-topped appearance such as one might fancy would 
arise from the wearing down of the edges to a shallow sulcus. 
