468 MK. p. W. BASSETT-SMITH ON [-^pr- 18j 



* placed laterally, the second small, central; third pair large, 

 spreading. Genital segment as large as the cephalothorax. 

 Abdomen small, hidden. Thoracic limbs very rudimentary. 



(1) Peeissopus dentatus. $ . 



Perissojnis dentatus Stp. & Liitk. Bidrag til Kundskab, 1861 , 

 p. 393, pi. xii. fig. 25. 

 communis Eath. Proc. U.S. N. H. Mus. 1887, x. p. 560. 

 Hosts : Carcharias sp. and G. obscurus. 



(2) Peeissopus armatus. $ . 



Lepidopus armatus Dana, Proc. Am. Acad. Arts & Sc. 1843, 



p. 60. 

 Perissopus armatus Stp. & Liitk. Bidrag til Kundskab, 1861, 



p. 394. 

 Host : Mustelus vulgaris. Eio Janeiro. 



(3) Peeissopus incisus. $ . 



CMamys incisus V. Ben. Bull. Acad. Eoy. Belg. 1892, p. 227, 

 pi. ii. fig. 1. 



Host : — ? Bay of Dakar, Senegal. 



Family III. DICHELESTIID^. 



The body is as a rule elongated, and the head small. The free 

 thoracic segments are simple (only exceptionally seen with dorsal 

 plates). Abdomen generally rudimentary. The anterior antennae 

 are slender, mostly with many joints up to 15, rarely short with 

 only 2 or 3 joints. Posterior antennae unciform or cheliform, 

 generally projecting beyond the border of the cephalothorax. 

 Mouth-parts as in Caligidce. Generally there are four pairs of 

 thoracic limbs, frequently short, stump-like, or suppressed, or the 

 posterior ones transformed into lamellar plates. Eye single, 

 median, or absent. Genital organs as in Caligidce. Male and 

 female only relatively different. The majority are capable of a 

 certain amount of locomotion. 



G. 1 . Anthosoma Leach. 



Head oval, infolding, broadest posteriorly. Two distinct dorsal 

 thoracic plates, and three pairs of large overlapping ones which 

 represent the limbs. Abdominal segment small, terminating in 

 two long caudal appendages. Anterior antennae long, multi- 

 articulate. Posterior antennae unciform, very large, and projecting. 

 Eostrum elongated. 



(1) Anthosoma ceassum. 2 • 



Caligus crassus Abgd. Mem. de Copenhag. 1794. 



„ imbricatus Eisso, Hist. Nat. Crust. Nice, 1816, p. 162, 

 pi. iii. fig. 13. 



