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



The carapace is about one-third of the length of the animal, and is anteriorly produced 

 to a laterally compressed rostrum that is once and a half as long as the carapace. The 

 dorsal surface is carinated over the gastric region and armed with two large teeth, one on 

 the pyloric and the other on the gastric region, and two others, equally distant from each 

 other, stand on the base of the rostrum, from the anterior tooth of which the rostrum is 

 smooth to near the apex, which is gradually curved upwards and furnished near the 

 extremity with two very small teeth. The under margin is largely excavate near the 

 ophthalmopoda, where it is very deep, and gradually narrows to the apical extremity, and 

 is armed with a series of eight teeth gradually decreasing in size anteriorly. The frontal 

 margin has no orbital tooth ; the first antennal is well developed, but the second antennal 

 is small and the fronto-lateral angle is rounded off. The rest of the carapace is smooth, 

 but evidences of lateral carinas exist in a rudimentary condition, corresponding with the 

 first and second antennal teeth. 



The pleon is dorsally smooth, excepting that the third somite, which is longer than 

 any of the others, projects posteriorly over the fourth. The three anterior somites have 

 the postero-lateral angle rounded, the fourth has it slightly angular, the fifth has it sharply 

 angular, and the sixth, which is longer than the fifth, is posteriorly produced to a sharp 

 tooth, anterior to which there is a deep excavation to receive the sixth pair of pleopoda. 



The telson gradually tapers to a rounded apex, the dorso-lateral angles being armed 

 with three small equidistant spinules. 



The ophthalmopoda are short and pyriform. 



The first pair of antennae (fig. 36) has the first joint of the peduncle excavate on the 

 upper surface, and furnished with a long stylocerite that reaches beyond the extremity of 

 the first joint; the two succeeding joints are together shorter than the first, cylindrical, and 

 unequal, the third being the shorter ; the flagella are nearly equal in length and shorter 

 than the rostrum. 



The second pair of antennae (fig. 3c) carries a long and gradually narrowing scapho- 

 cerite, the extremity of which is armed with a strong tooth ; the flagellum is broken off 

 at less than the length of the rostrum. 



The mandibles (figs. 3d, 3d') have a broad and bluntly serrate psalistoma, the anterior 

 angle of which consists of a large tooth, and the whole is continuous with the molar tubercle, 

 which is smooth on the anterior and coarsely serrate on the posterior margin ; from the 

 outer angle a two-jointed synaphipod arises which carries a strong bunch of short hairs at 

 the base, and similar hairs also stud the distal spatuliform joint. 



The first pair of siagnopoda (fig. 3e) is three-branched ; the inner branch is short, 

 rounded, and fringed with soft hairs and a few stout spines ; the second or middle branch 

 is broad, wider at the distal margin than at the base, and fringed with two or three 

 rows of strong spines ; the third or outer branch is short, curved, and bifid, one 

 extremity carrying a single fringed hair and the other several hairs. 



