106 BRITISH PARASITIC COPEPODA. 



Antennae large, as long as the antennules, and chele- 

 form or uncinate at the end, usually projecting 

 forward beyond the front of the head. The first and 

 second pairs of thoracic legs small and biramose, but 

 the fourth pair each composed of a single one-jointed 

 lamelliform plate. 



The male is somewhat similar to the female, but 

 smaller. 



1. Dichelestium oblongum (Abildgaard). 

 (Plate XXXI, figs. 7-18; Plate XLV, figs. 4, 5.) 



1794. Caligus oblongus Abildgaard. (1) vol. iii, p. 52, pi. v. figs. 4-11. 

 1804. Dichelestium sturionis Hermann. (61) p. 125, pi. v, figs. 7 & 8. 

 1838. Dichelestium sturionis Kroyer. (70) vol. i, p. 299, pi. ii, fig. 5, 5a. 

 1836. Dichelestium sturionis Rathke. (99a) Act. Akad. Leopold 

 Carol, vol. xix, p. 127, pi. xvii, figs. 1-17. 



1840. Dichelestium sturionis M. Edw. (43) p. 485, pi. xxxix, fig. 4. 



1905. Dichelestium sturionis T. Scott. (116) p. Ill, pi. v, figs. 17-24 ; 

 pi. vi, figs. 1-6. 



1906. Dichelestium oblongum Norman & T. Scott. (88) p. 215. 



Female. Body elongated, narrow ; carapace nearly 

 as broad as long and somewhat rhomboid in outline, 

 widest behind the middle, and with the sides bluntly 

 angulated ; it is also obscurely lobed in front and 

 narrowed and truncated behind. Thoracic segments 

 four, the first and second short and subequal, but 

 the first produced laterally into short rounded lobes 

 directed backwards, the second having the sides also 

 lobate but produced slightly outwards. The third 

 segment, which is rather longer than the preceding 

 one, widest behind, and with a slight constriction in 

 the middle. The fourth segment similarly constricted, 

 and somewhat longer than the third. The genital 

 segment about one and a half times the length of the 

 preceding segment and tapering slightly towards the 

 posterior end. Abdomen short. Caudal rami small ; 

 egg-strings long and narrow^ . 



Antennules moderately short and slender and com- 

 posed of eight subequal joints. Antennae stout, and 

 extending prominently in front of the carapace ; indis- 

 tinctly three- or four-jointed, the end joint slightly 



