REPORT ON THE CRUSTACEA MACRURA. 423 



Sergestes prsecollus, u. sp. (PL LXXVII. fig. 2). 



Very closely resembling Sergestes longicollus, but differing in certain details, of 

 which the following are the most important. 



The fifth somite of the pleon in Sergestes prsecottus has the posterior margin dorsally 

 produced to a point ; the sixth somite is not produced to a point posteriorly. 



The scaphocerite is broad and armed on the anterior margin with a subapical tooth ; 

 inner margin sparsely fringed with short hairs. The oral apparatus is a little in advance 

 of the centre of the carapace. 



The first pair of gnathopoda is rather more robust than in Sergestes longicollus, and 

 is produced to a truncated tubercle at the posterior angle of the coxal joint. 



The second pair of gnathopoda is tolerably long and robust ; the distal joints are not 

 more slender than the proximal, and are fringed with cilia. 



The first pair of pereiopoda is two-thirds the length of the second pair of gnathopoda, 

 and is not furnished with a prehensile apparatus at the ultimate articulation. 



The third and fourth pairs of pereiopoda are subecmal and terminate in a short and 

 fringed chela. 



The sixth pair of pleopoda has the outer plate furnished with a small tooth nearly 

 halfway from the distal apex ; the margin beyond the tooth being slightly excavated 

 and fringed with hairs, also the inner margin and both margins of the inner plate. 



The carapace in this, as in the preceding species, has the lower margin closely folded 

 beneath the ventral surface and deepens posteriorly. 



Length, 25 mm. (l in.). 



Habitat. — North Pacific Ocean. 



Observations. — The specimen is one of those that corresponds closely with Sergestes 

 tenuiremis, but differs from it and from Sergestes longicollus in the form of the posterior 

 pair of pleopoda, which is armed on the outer margin with a tooth more distant from the 

 distal extremity of the plate, and has the space beyond it slightly concave. These species 

 and Sergestes junceus all agree with Sergestes tenuiremis in having the distance between 

 the oral appendages and the antennal or frontal region considerably prolonged, and 

 suggest an approximation to the genus Lcucifer, with which name von Willemoes Suhm 

 has labelled one of the specimens that was mounted for microscopic use. 



Sergestes semiarmis, n. sp. (PL LXVII. fig. 1). 



Rostrum sharp, straight, armed on the upper surface with a small tooth, and reaching 

 to about half the length of the first joint of the peduncle of the first pair of antennae. 

 Carapace nearly a third of the length of the animal, having the frontal margin furnished 

 with a strong tooth on the outer side of the first pair of antennae. 



