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



with a series of small spines on the same side, that increase in length as they approach 

 the distal extremity, where the ultimate spine nearly equals the unguis in 

 importance (fig. lm). 



The pleon is smooth and the telson is triangulate. 



Habitat. — Atlantic Ocean, on Gulf-weed. 



In the open ocean near the Azores by M. Reynaud (Milne-Edwards). 



In the Atlantic Ocean, lat. 30° to 35° ; common on the Sargasso weed (Stimpson). 



The typical specimens in the Challenger collection were taken near Bermuda, 

 in April 1873, in large numbers, many hundreds, of both sexes, in apparently equal 

 proportions, associated in equal abundance with Palsemon natator. On the 4th of May 

 1876, on the homeward passage of the ship, between Stations 355 and 354, south of 

 the Azores, about a dozen others were taken, and some among these showed a variation 

 which enabled me more readily to determine the sexes, since the males generally 

 had the extremity of the rostrum less perfectly dentated, the first pair of antennas 

 with the outer branch thicker and longer, and the scaphocerite longer, and more 

 pointed. 



Palsemon fucorum, Fabricius, 1 undoubtedly belongs to this genus, and from the 

 statement that the rostrum is armed at the extremity with five teeth, I should have 

 believed it to be the original of this species had not the author stated that the carapace 

 is smooth (" Thorax lee vis "), whilst a small tooth stands above the gastric region in 

 Latreutes ensiferus. 



On one specimen I found a small species of Bopyrus which I name Bopyrus 

 latreutis, since it differs from Bopyrus squillarum, Latr., in having a rounded caudal 

 extremity, as well as in size. 



Latreutes planus, n. sp. (PI. LXXXIX. fig. 5). 



Carapace dorsally unarmed and produced to a robust rostrum which is deep, 

 laterally compressed, anteriorly pointed, and serrate. Dorsal surface of the carapace 

 smooth and free from ornamentation. Pleon dorsally smooth, posterior extremity of 

 the sixth somite produced to a small tooth. 



1 Suppl. Entom. Syst, p. 404. 



