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



From the tiljove measurements, when comparecl with tliose of SeroUs australiensix 

 (ante, j). 68), it wOl appear that SeroUs elongata is rather narrower, the length being 

 proportionately greater than the breadth. 



The main difference, however, between tlu- two species is the development of 

 tubercles upon the dorsal surface of the body ; SeroUs austraUensis is to be distinguished 

 from all other species of the genus by the immense number of tubercles upon the 

 segments of the body, and also upon the caudal shield ; in SeroUs elongata the dorsal 

 surface of the body is by comparison almost smooth ; this cannot be owing to the 

 difference of age ; the female specimen of SeroUs elongata, although actually smaller 

 than SeroUs austraUensis, is perfectly mature, with fully-developed ovigerous lamellfe ; and 

 as no other species that I have been alile to examine undergoes any change, except mere 

 increase in size, as soon as it has attained to maturity, there is no reason to suppose that 

 Sei'oUs elongata is peculiar in that respect. As in SeroUs austraUensis, each of the 

 segments of the body is furnished with a curved hook -like spine in the middle line ; a 

 row of short tubercles occupies the hinder portion of each of the segments, and is 

 prolonged on to the epimera ; besides these there appear to be a few scattered 

 tubercles over the rest of the segments and the epimera, which are very inconspicaous, 

 and contrast with the strongly tulierculated surface of the body in SeroUs austraUensis. 



The caudal shield has the same general shape that it has in the last mentioned species, 

 with serrated margins and a longitudinal carina. There is also a lateral carina on either 

 side bearing a short spine, which is situated about half way down the caudal shield, and a 

 little below the place where the uropoda are attached, and terminating at the end of the 

 l)ody by becoming fused with the central caiina ; as in SeroUs austraUensis, these lateral 

 carinse are serrated. Between these and the central carina is a short ridge running 

 obliquely towards the margin of the caudal shield from a point a little below and to one 

 side of the commencement of the central carina ; the general surface of the caudal shield 

 is smooth, and there are only present a few scattered tubercles, especially developed in 

 the neighbourhood of the two lateral carinas. 



Port Jackson, Sydney, 30 fathoms. 



14. SeroUs longicaudata, F. E. B. (PL VII. figs. 8-10 ; PI. VIII. figs. 1, 2). 

 SeroUs longicaudafu, Y. E. Beddard, Proc. Zool. Soc. Lond., 1884, pt. iii. p. 336. 



Of this species the Challenger obtained one immature female ; its length is 7 nun., 

 its breadth 5 mm. 



The general form of the body is peculiar, and unlike that of th(> typical members of 

 the genus; the anterior portion of the body, comprising the head, thorax, and free abdominal 

 segments is almost completely circular, and the caudal shield jirojects backwards for a 

 considerable distance, being proportionately longer than in any other of the species 



