1408 THE VOYAGE OF H.M.S. CHALLENGER. 



For the original definition of the genus Themisto, see Note on Guerin, 1828 (p. 133). 

 Bovallius in 1887, finding that the name Themisto was preoccupied, changed it into 

 Euthemisto, for which he gives the following definition : ' — 



" This genus differs from Hyperia by the narrow, gauge-shaped carpal process of the 

 second pair of pereiopoda [Second Gnathopods] ; the carpus of the first pair being broad 

 but not produced. From Parathemisto it differs by the strong development of the fifth 

 pair [Third Perseopods] ; this latter characteristic however is not of any higher value, as 

 there are transitions between the two genera." 



It may be added that Euthemisto is distinguished from Hyperia, Hyperoche, and 

 Hyperiella by the stronger development of the inner plate of the maxillipeds. 



Euthemisto bispinosa (Boeck). 



1870. Themisto bispinosa, Boeck, Crust, amph. bor. et arct., p. 8 (88). 



1872. „ „ Boeck, De Skand. og Arkt. Ainph,, p. 87, pi. i. fig. 4. 



1887. Euthemisto bispinosa, Bovallius, Systematical List of the Amph. Hyper., Bihang till K. 



Svensk. Vetensk. Akad. Handl., Bd. 11, No. 16, p. 22. 

 1887. „ „ Arctic and Antarctic Hyperids, Vega-Exped., Bd. iv. p. 569, pi. xlvi. 



figs. 97-103. 

 1887. Euthemisto compressa (pars), Hansen, Malacostraca marina Groenlandise occidentalis, 



p. 59. 



In large specimens there is a bulge of the frontal margin on either side just below the 

 rostral point ; the back is carinate along both the perseon and pleon, developing a dorsal 

 tooth produced backwards from the centre of the hind margin in each of the last two or 

 three segments of the perseon, and the first three or four of the pleon, in large specimens 

 the tooth being very prominent in the last two segments of the perseon and the first two 

 of the pleon ; the smaller the specimen the less important is the size of the teeth. 



In Boeck's very brief account of the species it is stated that the last three pairs of 

 perseopods have the first joint very narrow, not dilated, and of the third perseopods in 

 particular it is said that the first joint is only slightly dilated, with a convex front and 

 straight hind margin, and that the limb itself is little longer than in the following pairs. 

 In the Challenger specimens, if they be rightly referred to this species, the third 

 perseopods are very considerably longer than the fourth or fifth, in agreement with Boeck's 

 figure ; the first joint is of the shape usual in the genus, being channelled behind. 



Bovallius says of this species, " it is characterized by the carinated, serrated dorsal 

 side, by the carpal process of the second pair of pereiopoda [Second Gnathopods] being 

 shorter than the metacarpus, provided with a terminal spine, by the irregularly triangular 

 carpi of the third and fourth pairs [First and Second Perasojyods] being as long as the 

 metacarpi [fifth joint], by the very short exterior rami of the uropoda, and by the small 

 semicircular telson, not equalling a fifth of the length of the peduncles of the last pair of 



1 Arctic and Antarctic Hyperids, p. 568. 



