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Part ILL. — Eighteenth Annual Report 



This, like other species of Lepeoplitlieirus, exhibits a certain amount of 

 variation, but full-grown specimens may usually be distinguished by the 

 form of the ventral fork. L. hipp>oglossi appears to be found principally 

 on the halibut, and is not uncommon. I have found a slightly immature 

 specimen on a torsk, Brosmius brosme, in Aberdeen Fish Market, but 

 probably it had been accidentally transferred to the torsk by contact of 

 that fish with a halibut. 



Lepeoplitlieirus tliompsoni, Baird. (PI. V., figs. 43-45.) 



1850. Lepeoplitlieirus tliompsoni, Baird, op. cit., p. 278, PI. 

 XXXIIL, fig. 2. 



1899. Lepeoplitlieirus tliompsoni, Basset-Smith, Proc. Zool. Soc. 

 Lond. (April 1899), p. 455. 



This is a smaller species than the last ; the female represented by the 

 drawing (fig. 43) is about one-third of an inch (8*5 mm.) in length. 

 In this species the last segment of the thorax is sub-quadrate in outline, 

 rather longer than broad, and increases slightly in width posteriorly. 

 The abdomen is elongated, and its thickness increases to a slight extent 

 for a short distance beyond the middle, when a slight decrease begins and 

 where also a small constriction is sometimes visible. The caudal segments 

 are very short. 



The antennae of Lepeoplitlieirus tliompsoni are armed with stout and 

 strongly-hooked claws (fig. 45). The mandibles are somewhat similar to 

 those of Lepeoplitlieirus pectoralis. The sternal fork is also somewhat 

 like that of the same species, but the branches of the fork are scarcely so 

 much dilated (fig. 44). The fourth pair of thoracic feet are distinctly 

 three-jointed, and moderately stout; they each bear three terminal setae, 

 and a seta or spine at the outer distal angle of the first and second joints, 

 but that on the first joint is very minute. The fifth pair, which are oval 

 in outline, are very small and situated below and slightly anterior to the 

 bases of the ovisacs. 



Habitat. — On the gills of turbot, Bothus maximus, captured in the 

 Firth of Forth, the Firth of Clyde, and on the gills of turbot examined 

 in the Fish Market at Aberdeen. 



Lepeoplitlieirus stromi } Baird. (PI. YL, figs. 3-8.) 



1847. Caligus stromii, Baird, Trans. Berw. Nat. Club (1847). 



1850. Lepeoplitlieirus stromii, Baird, Brit. Entom., p. 274, PI. 

 XXXII., figs. 8 and 9. 



We have obtained this copepod on salmon, Salmo salar, captured in 

 Montrose Bay and Bay of Nigg (Aberdeen). I have seen no specimens 

 from the Firth of Forth or the Firth of Clyde, but they will doubtless be 

 found on salmon captured within these estuaries as well as elsewhere. 



Lepeoplitlieirus stromi has the abdomen proportionally rather more 

 elongated than that of L. thompsoni, and the ovisacs are usually very 

 long and slender. The dorsal surface in this species has a curious metallic 

 lustre, different from most of the others of the same genus. Males 

 appear to be comparatively scarce. 



The branches of the sternal fork are moderately short and stout, and 

 are broadly rounded at the ends (fig. 5). The fourth pair of thoracic feet 

 have the branches three-jointed and provided with four short setae; the 

 outer distal angle of the first joint is apparently not provided with a seta 

 in this species, but is simply rounded. The fifth pair of feet are broadly 



