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



" First and Second Gnathopods alike in form, thin, narrow ; the hand subcheliform. 



" Last three paii's of Pergsopods successively longer ; the first joint more or less 

 dilated behind. 



" Uropods biramous ; the first and second pairs with the outer ramus shorter than 

 the inner ; the third pair with the two rami of almost the same length, laminar, setose 

 on the margin. 



" Telson long, cleft." In Tiron, however, the hand of the gnathopods is not 

 subcheliform. 



Genus Syrrhoc, Goes, 1865. 



1865. Syrrhoe, Goes, Crust. Amph. Maris Spetsb., p. 12. 

 1870. ,, Boeck, Crust. Amph. bor. et arct., p. 67. 

 1876. „ Boeck, De Skand. og Arkt. Amph., p. 471. 



For the brief original definition of the genus, see Note on Goes, 1865 (p. 357). The 

 following more expanded definition was given by Boeck in 1870 : — 



" Mandibles very thick, robust, apically little dentate ; molar tubercle prominent, not 

 robust. 



"Eyes confluent. 



" Side-plates of moderate size. 



" First and Second Griathopods with the hand short, subcheliform ; the second 

 gnathopods longer than the first. 



" The last three pairs of Peneopods elongate, narrow ; first joint more or less dilated 

 behind. 



" First and Second Uropods with the outer ramus much shorter than the inner. 



" Third Uropods with the rami foliaceous, subequal. 



" Telson cleft." 



In the description of the subfamily, Boeck states that the lip is insinuate at the apex, 

 which does not appear to be the case with the Challenger species, Syrrhoe papyracea. 

 In the generic definition Boeck speaks of the mandibles as with " tuberculo molari pro- 

 minenti, non robusto," while in the specific description of Syrrhoe crenidata, he says 

 " Tyggeknuden er bred, men kun lidet fremstaaende " ; in the Challenger species the 

 molar tubercle is both robust and prominent. Norman in 1869 gives a definition of 

 Syrrhoe, including the character, " Gnathopods not subchelate," but this evidently has 

 reference to the species Syri-hoe hamatijjes, Norman, which, as well on account of the 

 gnathopods as of the short fifth perseopods, ought to be transferred to the genus Tiron, 

 Lilljeborg. Gerstaeeker in 1886 makes Syrrhoe a synonym of Tiron, which he says 

 diS"ers from Urothoe " durch das nicht in eine Greifhand endigende erste und zweite 

 Beinpaar." Yet in this particular character Tiron is as much separated from Syrrhoe as 

 it is from Urothoe. 



