142 BRITISH PARASITIC C0PEP0DA. 



In the young but sexually mature stage the Lernasidse do 

 not differ greatly from the preceding families. The sexually 

 mature young are furnished with two pairs of antennas ; the 

 posterior pair usually end in strong hooks which project 

 beyond the forehead ; the maxillipeds are small and feeble, 

 and the four pairs of thoracic legs are tolerably developed. 

 The abdomen is usually rudimentary, and a median eye- spot 

 is present. In the larval stages the young approximate more 

 closely to Cyclops and are more or less free-swimming. 



G-enus 27. LERN^A Linnaeus, 1767. 



Head globular, slightly recurved, with the apex 

 rounded or conical, and provided usually with three 

 chitinous, more or less branched and horn-like append- 

 ages, two of them lateral and one median and dorsal. 

 Thorax in the form of a moderately long, slender, and 

 fiexuous neck, which gradually becomes merged into 

 the genital segment. Genital segment moderately 

 enlarged, elongated and subcylindrical, and usually 

 more or less abruptly bent upon itself, somewhat like 

 the letter S. Egg-strings elongated and slender, and 

 twisted into involved roundish, masses under the pos- 

 terior portion of the genital segment. Several of the 

 cephalothoracic appendages becoming, in the fixed stage 

 of the female, degenerate and rudimentary or obsolete ; 

 the first maxillipeds however retain their form, and 

 are furnished with terminal hooks ; the four pairs of 

 thoracic legs are also persistent, and may be seen on 

 the ventral aspect behind the subglobular head with the 

 aid of a low-power objective. 



The various species of Lernsea are securely anchored to the 

 host by the cephalic horns. 



1. Lernsea branchialis Linnseus. 

 (Plates XLII & XLIII.) 



1767. Lernsea branchialis Linn. (78) vol. i, pt. 2, p. 1092. 

 1850. Lernsea branchialis Barrel. (4) p. 344, pi. xxxv, fig. 12. 



1900. Lernsea branchialis T. Scott. (112) p. 161, pi. vii, figs. 11, 12. 



1901. Lernsea branchialis A. Scott. (108) p. 33, pis. iv and v. 



Female. — Head apiculated or conical, slightly re- 

 curved and provided with strong, branching, horn-like 



