62 BRITISH PARASITIC COPEPODA. 



single joint, somewhat longer than broad, and scarcely 

 equal to one-third of the length of the genital segment. 

 Caudal rami of moderate size. 



Antennules tolerably stout, and composed of two 

 subequal joints. Antenna3 with the end joint in the 

 form of a strongly-hooked claw. Sternal fork small 

 with tolerably short and slender rami which are 

 moderately curved and somewhat divergent. The 

 fourth pair of thoracic legs consisting each of a single 

 joint, small and rudimentary and furnished with three 

 spiniform setae, two of them short and subequal, and 

 the other tolerably elongated and plumose. The fifth 

 pair in the form of minute setiferous plates near the 

 postero-lateral corners of the genital segment. Length 

 about 3*6 mm. 



Male. The male is rather smaller than the female, 

 and differs from it chiefly by the small size of the 

 genital segment. The carapace is also rather wider in 

 proportion to the length, while the second maxillipeds 

 are larger and form more powerful grasping organs. 



Habitat. Parasitic on the three-bearded rockling, 

 Onos (Motella) tricirrata Brun., and usually found 

 adhering to the inner surface of the gill-covers. 

 Plymouth (Bassett- Smith). Irish Sea, Barrow Channel, 

 and at Port Erin, Isle of Man (A. Scott). Dunbar, at 

 the month of the Forth estuary, and near Aberdeen 

 (T. Scott). 



This species is easily distinguished by the rudimentary 

 character of the fourth pair of thoracic legs in both sexes. 

 From the records of the species published hitherto it seems 

 probable that the distribution of the Pseudocaligus will he 

 coextensive with that of the fish mentioned. 



Genus 6. SCI^ENOPHILUS P. J. van Beneden, 1852. 



Carapace somewhat similar to that of Cali<jn*. 

 Frontal plates distinct and provided with lunulse. 

 Free thoracic segment small. Genital segment narrow 

 and considerably elongated. Abdomen slender and 

 of great length. Caudal rami short. Mouth append- 



