112 



Part III. — Twenty -third Annual Report 



Habitat. — Taken from a sturgeon, Acipenser sturio, captured about 

 16 miles S.E. by E. of Aberdeen and brought into the Aberdeen Fish 

 Market, December 29, 1904. The same species of Dichelestinm has also 

 been found by my son, Andrew Scott, on the gills of a sturgeon 

 captured near Barrow-in-Furness, Lancashire. I am indebted to Mr. 

 Bowman of Aberdeen for this further addition to the marine copepod 

 fauna of Scotland. 



The structure of the mouth organs, and especially of the mandibles, 

 indicates a close relationship of Dickelestium with the Caligidae. 



Genus Anthosoma, Leach (1816). 



Anthosoma crassum (Abilgaard). PI. v., figs. 15 and 16. 



1794. Caligus crassus, Abgd., Mem. de Copenhagen, Act. Soc. 

 Nat. Havn. 



1837. Anthosoma Smithi, Kroyer, Naturji. Tidsskr., 1st B., p. 



295, Tab. ii., figs. 2 and 2a ($). 

 1850. Anthosoma Smithi, Baird, Brit. Entom., p. 296, pi. xxxiii., 



fig. 9. 



1861. Anthosoma crassum, Steenstrup and Lutken, Bidrag til 

 Kundskab, p. 397, pi. xxii., fig. 24 (tf). 



This interesting species was found on a shark, supposed to be a 

 Porbeagle shark, Lamna comubica, captured off the coast of Scotland by 

 one of the trawling steamers that make only short runs from Aberdeen. 

 The steamer, which captured the shark in October 1904, is one of those 

 belonging to Mr. Davidson, Aberdeen, and is locally known as a " short 

 tripper." Two specimens of the Anthosoma were obtained \ one of them 

 is a female with ovisacs, the other, which is smaller, is probably a male. 

 The drawings, figures 15 and 16 on plate v., represent a dorsal and 

 ventral view of the female. This specimen measured about 15 millimetres 

 exclusive of the ovisacs, and about 62 millimetres — nearly 2^ inches — to 

 the extremity of these appendages. 



The female, which is tolerably elongated, appears, when seen jrom 

 above to be of an ovate outline ; it is narrow in front, and a brownish 

 horny shield, which gradually expands towards the posterior end, covers 

 the head and a considerable portion of the thorax ; an obscure constric- 

 tion marks the junction of the head with the thorax ; two large foliaceous 

 elytraform, circular plates, the inner margins of which partly overlap each 

 other on the dorsal aspect, cover entirely the remaining portion of the 

 thorax not covered by the dorsal shield, and also the abdomen and furcal 

 joints. These plates are ornamented by numerous minute scattered 

 punctures or depressions, as shown in the drawing (fig. 15). 



The antennules are short, slender, and composed of six joints which are 

 very sparingly setiferous; but the antennae — described by Baird as the 

 first pair of footjaws — are strong and powerful ; they are longer than the 

 antennules and composed of three joints, and armed with strong, terminal, 

 hook-like claws. 



The first maxillipeds are slender and feeble, and appear to consist of 

 three joints ; they are provided with a small, terminal, claw-like -spine. 



The second maxillipeds are short, very stout and powerfully clawed. 



The thoracic legs are in the form of thin and broadly foliaceous plate, 

 each having a distinct notch on the inner margin. 



The abdomen is short and the furcal joints narrow and moderately 

 elongated, as in figure 16, which shows the ventral aspect of the 

 specimen. 



The shield is of a chitinous texture, of a brownish colour on the sides, 



