Mr. C. T. Regan on llexanchus griseiis. 571 



to Junesiella in general appearance. Antennules (anterior 

 antennae) short and composed of six joints. Antennae (poste- 

 rior antenna?) with the outer ramus well developed, three- 

 jointed, middle joint short. Mandibles distinctly two-branched. 

 First pair of thoracic feet with both branches three-jointed, 

 the inner being more elongated than the outer branches ; 

 other thoracic feet somewhat similar in structure to those of 

 Jonesiella. 



Thompsonula hycence (I. C. Thompson). 



1889. Jonesiella hycB7ice, I. C. Thompson, Proc. Biol. See. Liverpool, 



vol. iii. p. 193, pi. ix. figs. 1-10. 

 1893. Jonesiella hycence, T. Scott, Eleventh F. B. Eeport, pt. iii. p. 202, 



pi. iii. figs. 1-6. 



In this species the basal joint of the short six-jointed 

 antennules is very stout and comparatively large ; it extends 

 forward, while the remaining joints curve outwards, so that 

 tlie last three are nearly at right angles to the basal joint. 

 The rostrum, which extends forward between the basal joints 

 of the antennules, reaches to beyond the extremity of these 

 joints. The furcal joints are extremely short, and as the 

 last abdominal segment is tolerably broad, the posterior has 

 an abruptly truncated appearance. 



Further particulars concerning this interesting species will 

 be found in the papers referred to above. 



LXIV. — Note on Hexanchus griseus. 

 By C. Tate Regan, B.A. 



The British Museum has recently received, from Captain 

 Alan Ovvston, a shark of the genus Hexanchus, captured in 

 Japanese seas. 



The specimen measures 2100 mm. in total length, and for 

 comparison with it I had a small example (600 mm.) of 

 Hexanchus co7-inus, Jordan and Gilbert, from the Pacific 

 Coast of the United States, as well as specimens of the 

 Atlantic H. griseus. 



The Japanese fish closely resembles the one named 

 H. corinus in most respects, but differs notably in tlie dentition. 

 In the lower jaw the median tooth has about 4 distinct cusps 

 on each side and 3 minute ones on the upper edge, whilst the 

 lateral teeth have from 8 to 10 cusps each. In the upper jaw 



