REPORT ON THE CRUSTACEA MACRURA. 435 



stage the posterior pair is wanting in most of the young of Sergestes, I prefer to reserve 

 my opinion until I have had an opportunity of examining an adult form ; I am the more 

 inclined to do so on account of a specimen having been taken in the West Pacific, which, 

 though evidently in a younger stage, corresponds with it in almost every important 

 detail, having the posterior two pairs of pereiopoda more advanced in development, 

 although still in a saccular condition. It is in the Mastigopus stage and is described at 

 page 376. 



Sergestes serrxdatus, Kroyer. 



Sergestes serrulatus, Kroyer, Monograph. Fremstilling af Krasb. Sergestes, pp. 52, 65, Tab. iv. 

 fig. 12, a-g. 



" Eostrum straight, rudimentary ; furnished with three or four distinct teeth on the 

 upper margin. 



" Ophthalmopoda reaching to the extremity of the first joint of the peduncle of the 

 first pair of antennae, clavate, three times longer than broad. 



" First pair of antennae having the peduncle equal in length to the carapace, or even 

 exceeding it, being a fourth of the length of the animal ; first joint broad, deeply ex- 

 cavated, and furnished with a strongly pointed tooth. 



" Second pair of antennae having the scaphocerite narrow, sublinear, three times longer 

 than the last thick joint of the peduncle, and nearly reaching to the distal extremity of 

 the second joint of the first pair of antennae. 



" Sixth somite of the pleon nearly equalling the fifth part of the animal in length ; twice 

 as long as broad, equalling at least the length of the fourth and fifth somites combined, 

 and exceeding that of the first and second together ; nearly twice as long as the telson. 



" Pleopoda moderate. 



" Ehipidura armed with a tooth on the outer margin about one-third from the apex. 



" Habitat. — Greenland " (Kroyer). 



Sergestes caudatus, Kroyer. 



Sergestes caudatus, Kroyer, Monograph. Fremstilling af Kraab. Sergestes, pp. 54, 68, Tab. v. 

 fig. 14, a-d. 



" Rostrum large, equalling one-fourth (?) part of the carapace in length, and furnished 

 on the upper surface with six or seven small teeth. 



" Ophthalmopoda very short, stoutly pyriform, scarcely reaching to the extremity of 

 the first joint of the peduncle of the first pair of antennae, having the ophthalmus 

 slightly distinct from the pedicle, and nearly half the length of the ophthalmopod. 



" First pair of antennae having the peduncle about two-thirds the length of the carapace, 

 and equal to a fifth part of the entire length of the animal. First joint very long, longer 

 than the second and third combined ; third very short. 



