324 THE VOYAGE OF H.M.S. CHALLENGER. 



The first pair of pleopoda is not determinable ; the four following are short and 

 biramose. 



The branchiae have not been examined because the specimen is unique and of excep- 

 tional character. 



I believe the specimen to be an immature form, but in its general appearance it 

 approximates more to that of Aristeus than to any other, but when other specimens 

 have been taken and an opportunity has been afforded for an examination of the 

 branchiae, we shall be in a better position to determine with confidence its natural 

 position in the order. 



Peteinura gubernata, n. sp. (PI. LIIL). 



Viewed laterally, the carapace triangulate, posteriorly deep, anteriorly narrow. 

 Rostrum, though broken off at the extremity, is much longer than the carapace, probably 

 nearly as long as the animal, and is spinous or denticulated above, below, and along the 

 sides from base to tip, the smaller teeth being towards the apex and the larger at the 

 base on the upper surface ; the posterior two are articulated spines, while all the others 

 appear to be rigid points. One large spine-like tooth stands above the orbital margin, 

 one further in, on the antennal region ; six are implanted on the branchial region, three 

 anterior and superior, and three inferior and posterior, of which the posterior is by far 

 the longest. 



The pleon has the first five somites subequal in length, the three posterior ones 

 decreasing a little in length and depth. The dorsal surface of each is surmounted with 

 a long spine-like tooth ; the posterior margin is furnished laterally with a small tooth 

 halfway between the dorsal and lateral margins ; the lateral margin is posteriorly produced 

 to a small point, and the ventral surface in the median line is produced to a short strong 

 tooth, directed infero-posteriorly. The sixth somite is long, narrow and subcylindrical ; 

 it is about as long as the four preceding somites combined ; the postero-dorsal margin is 

 produced to a large spiniform tooth, broad at the base and acute at the point ; at each 

 side of the base is a strong but slender tooth, and the postero-ventral surface is armed 

 with a strong and slender tooth that projects posteriorly between the basal joints of the 

 rhipidura. 



The telson is nearly as long as the sixth somite and terminates in a sharp point. 



The ophthalmopoda are short and pyriform, the ophthalmus being much broader 

 than the stalk, and the whole organ gradually tapering to the base. 



The first pair of antennas has a three-jointed peduncle, the length of which from the 

 extremity to the base is about half the length of the carapace. The first joint reaches 

 beyond the extremity of the ophthalmopod and is armed on the outer surface near the 

 base with a sharp tooth (stylocerite). The second joint is about one-third the length of 



