of the Fishery Board for Scotland. 



265 



strongly-pointed processes; abdomen, small; caudal furca, short (fig. 11); 

 antennules, scarcely reaching to the end of the thorax, and composed of 

 twenty-four joints, the proportional lengths of which are shown by the 

 formula (see also figure 2) — 



7-6'3-4-4-4-5-6-4-5 - 5' 6 - 1 • 7* 6 - 6 - (i- 5- 4* 4 - 4' 5* 5' 3 

 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 



The antennas are somewhat similar to those of Pseudocalanus elongatus, 

 but the secondary branches are scarcely so elongate (fig. 3). The mouth- 

 organs and swimming feet are all more or less similar to the same appen- 

 dages in Pseudocalanus elongatus as shown by the figures (figs. 4-10). 



Description of the male. — The structure of the male of Bradyidius 

 exhibits a greater amount of divergence from that of the nearly-related 

 Pseudocalanus than the female does. The number of joints of the male 

 antennule (fig. 12) is twenty-two on the left side, the eighth and tenth 

 joints being each apparently composed of two coalesced joints. The right 

 antennule is similar to the left, except that the seventeenth and eighteenth 

 joints appear to be joined together so as to form only one joint. The pro- 

 portional lengths of the joints of the left antennule are shown in the 

 formula — 



6-5-3-3-3-3-3-7-4-8 - 5' 6 ■ 1 • 2 - 2 - 2- 6 - 6 - 5- 6 - 5 - 3 

 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 



The mandibles are more or less rudimentary, and they are without the 

 usual apical teeth ; they resemble the mandibles of Pseudocalanus elon- 

 gatus, but are not so elongate (fig. 13). The maxillae are more robust 

 than those of Pseudocalanus^ and more nearly resemble those of jEtidius, 

 but are somewhat dissimilar in certain details of structure and armature, 

 as shown by the figure (fig. 14), The anterior foot-jaws, which are to 

 some extent rudimentary, are considerably stouter than those of Pseudo- 

 calanus, and the armature of the marginal lobes is peculiarly modified 

 (fig. 15). The fifth pair of thoracic feet differ in structure from both 

 Pseudocalanus and jEtidius. In Pseudocalanus both feet are developed, 

 but each consists of a single branch ; in yEtidius only one single- 

 branched foot is developed, the other being entirely obsolete ; in the 

 present species, which in the structure of the fifth pair more nearly 

 rescn>bles JEtidius, one of the single-branched feet is developed, while 

 the other is very rudimentary, but is nevertheless quite distinct, as shown 

 by the figure (fig. 16). Fig. 17 is a drawing of the fifth foot of an 

 immature male. 



Habitat. — Firth of Clyde, Loch Fyne, and West Coast ; frequent (rare 

 on the East Coast). 



Remarks. — This Copepod has occupied our attention for a considerable 

 time. It was felt that it could not be retained in the genus to which it 

 had been ascribed, but, owing to the structural details being somewhat 

 difficult to work out, the study of it was delayed. Last year Dr. "W. 

 Giesbrecht, the eminent zoologist of Naples Marine Station, published a 

 preliminary note on the species. He described a few of its more 

 important characters, and at the same time instituted the new genus — 

 Bradijidius — for its reception. Previous to that, however, the series of 

 drawings included in the present paper had all been prepared, but the 

 pressure of other work had delayed their publication. We are very 



