CALIGUS DIAPHANUS. 61 



abdomen is composed of two subequal, angular 

 segments, and is only equal to about one-sixtli of the 

 entire length. 



Habitat. Parasitic on various species of gurnards 

 (Trigla). Belfast (W. Thompson). Found on the inner 

 surface of the operculum of Trigla hirundo and Trigla 

 cuculus at Plymouth (Bassett- Smith). On Trigla spp., 

 Firths of Forth and Clyde (T. Scott). Irish Sea 

 (A. Scott). 



The species is apparently not uncommon, but we have 

 only met with it on gurnards. 



Genus 5. PSEUDOCALIGUS A. Scott, 1901. 



Carapace large and scutiform ; frontal plates 

 moderately prominent, and provided with lunulse. 

 Grenital segment and abdomen as in C aligns. Cephalo- 

 thoracic appendages also similar to those of Caligus, 

 except that the fourth pair of thoracic legs are some- 

 what rudimentary, and consist each of a single small 

 joint, furnished with a few minute terminal bristles. 



This genus has, in its general appearance, a close 

 resemblance to G aligns. 



1. Pseudocaligus brevipedes (Bassett-Smith). 

 (Plate IX, figs. 6-9 ; Plate X, figs. 1, 2.) 



1896. Caligus brevipedes Bassett-Smitli. (6) p. 11, pi. iii, fig. 1. 



1901. Pseudocaligus brevipedes A. Scott. (107) p. 350, pi. ii, figs. 1-6. 



1902. Pseudocaligus brevipedes T. Scott. (114) p. 291. 



1906. Pseudocaligus brevipedes Norman & T. Scott. (88) p. 207. 



Female. Carapace suborbicular, about as long as 

 broad, and equal to rather more than half the entire 

 length of the animal. Frontal plates well developed, 

 lunulse of moderate size. Free thoracic segment small. 

 Grenital segment subquadrangular, and about half as 

 long as the carapace, the length rather less than the 

 width, and the lateral margins nearly straight, the pos- 

 terior end also subtruncated, and the postero-lateral 

 corners bluntly rounded. Abdomen consisting of a 



