REPORT ON THE CRUSTACEA MACRURA. 



39.3 



tilth a liitlc longer; ventral surface with no conspicuous prominence in the median line. 

 Sixth somite equal in length to the four preceding combined, and slightly projecting 

 posteriorly on the dorsal surface. 



Telson about half the length of the rhipidnra, armed at the extremity with two teeth, 

 one at each an°;le and one small one on the lateral margin. 



Ophthalmopoda quite half the length of the carapace, slender, clavate. 



First pair of antennae having the peduncle quite as long as the carapace, the first 

 joint the same length as the ophthalmopod, and furnished with a short stylocerite and a, 

 circular otocyst ; the second and third subequal, the two together being about equal in 

 length to the first. 



The second pair of antennas has the terminal joint of the peduncle reaching to two- 

 thirds the length of the ophthalmopod, and the scaphocerite as far as the middle of the 

 third joint of the peduncle of the first pair of antennae. 



The mandible has a two-jointed synaphipod, of which the first joint is very long and 

 the second short. 



The first pair of gnathopoda is tolerably robust, but the second, though long, is 

 slender. The pereiopoda are also long and slender, the chelae of the third and fourth pairs 

 being rather long. The fourth and fifth pairs are in a rudimentary condition, the fourth 

 being considerably loDger than the fifth. 



The first pair of pleopoda is long and slender ; the others rapidly decrease in length 

 posteriorly. The terminal pair, which forms part of the rhipidura, has the outer margin 

 furnished with a tooth about one-third distant from the extremity, on a level with the 

 end of the inner branch. 



Length, 9 mm. (0"3 in.). 



Habitat. — South of Australia, March 1874. 



This species is thus named because it has a tooth on the dorsal surface of the carapace. 

 That this tooth should be solitary is remarkable, but the closest inspection has failed to 

 show the presence of a second, which not infrequently exists in some species. Neglecting 

 the value of the dorsal tooth, the animal approximates to Sergestus corniculum, from 

 which, however, it further differs in the greater length of the ophthalmopoda and 

 antennae, as compared with Kroyer's figure and description, which more closely resembles 

 the figure of Sergcstes corniculum given on PI. LXXV. fig. 1 of this Report. 



PMPINE 

 BIOLOGIC/ 

 LABORATO 



LiB RAF 



W00Q3 HOLE, I 

 W. H. 0. 



Sergcstes laterodentatus, n. sp. 



Carapace one-fourth of the length of the animal, including the telson and excluding the 

 rostrum. Rostrum long, slender, and horizontally straight, half as long as the carapace. 

 Frontal margin armed with a tooth just above the first pair of antennae, or between it 



