. Mandible segment i with a strong spine, but without molar process; exopod with five setae; endopod an undivided plate, with six setae or spines. Stage III, R. cornutus. Length 0-65-0-70, average o-66 mm. Body more elongated, the length about 3J times greatest width. Furcal region (Fig. 2 C) cleft, each branch bearing a short spine on ventral surface, a terminal spine, and an inner terminal soft seta. The right spine is longer than the left, but only about one-tenth length of body. Antennule with six terminal setae, but no aesthete. (Fig. 2B.) Antenna, exopod with eight setae. There is no tra
. Mandible segment i with a strong spine, but without molar process; exopod with five setae; endopod an undivided plate, with six setae or spines. Stage III, R. cornutus. Length 0-65-0-70, average o-66 mm. Body more elongated, the length about 3J times greatest width. Furcal region (Fig. 2 C) cleft, each branch bearing a short spine on ventral surface, a terminal spine, and an inner terminal soft seta. The right spine is longer than the left, but only about one-tenth length of body. Antennule with six terminal setae, but no aesthete. (Fig. 2B.) Antenna, exopod with eight setae. There is no trace of the maxillule. /\ Stage IV. Length: R. nasutus, 0-82- 0-89, average 0-85 mm.; R. cornutus, i-o mm. Body now very slender, five times as long as wide. Furcal region with two additional pairs of lateral spines. In R. nasutus the furcal spines have scarcely increased in length, so that the right spine is now shorter in proportion to the body, and not greatly longer than the left one (62 : 49). In R. cornutus it is nearly one-third of the length of the body (60 : 195) and about 21 times as long as the left spine (57 : 22). Mandible with strong molar process on coxa. Antennule with eight setae and aes- thete, arranged thus: In some specimens of R. cornutus the maxillule Fig. 6. Rhincalanus cornutus. Nauplius, stages V and VI. « represented by a slight fold with a A, upper lip, stage VI, showing arrangement of hairs on small projecting spinule, but I have body wall; B, mandible, stage V. seen no trace of it in R. nasutus. Stage V. Length: R. nasutus, 1 mm.; R. cornutus, 1-2 mm. Antennule with 7-A-4 terminal setae. Maxillule distinct, as a small fold bearing a small seta. Maxilla traceable as a faint fold with a minute spine. Body distinctly divided into an anterior region including the somite of the maxilla, 1 The arrangement of the setae on segment 3 may be conveniently expressed in this way: the first number being the setae behind the aesthete (A), and the second tho
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
