3o8 DISCOVERY REPORTS 



(2) Each of the thoracic and first three abdominal segments has the median dorsal 

 posterior border produced into a spiniform process, which is much larger in 5. exigua 

 than in S. carinata. 



(3) The median posterior border of the head is also produced into a spiniform process 

 in both species ; but in S. carinata this process is Y&Yy small and does not extend beyond 

 the head segment, whereas in S. exigiia it is produced backwards to about the middle 

 of the third (first free) thoracic somite. 



(4) In both species the first three free thoracic somites are separated from their coxal 

 plates by sutures. In 5. carinata the coxal plates of the seventh thoracic somite extend 

 beyond the ends of the pleural plates, which are very short and hardly extend beyond the 

 anterior margin of the terminal segment. In S. exigua they are short and do not ex- 

 tend beyond the pleural plates of the second and third abdominal segments. The pleural 

 plates of the third abdominal segment in S. exigua reach to the attachment of the 

 uropod ; those of the second are a little shorter. 



(5) The terminal segment of S. exigua is broader than long and roughly five-sided, 

 with a median dorsal and two lateral carinae, the latter lying midway between the 

 median carina and the lateral margin of the terminal segment, and not extending to the 

 posterior end of the segment. The terminal segment of S. carinata is roughly triangular, 

 longer than broad, with its posterior extremity truncate, and with a median and two less 

 pronounced lateral carinae which run parallel with the lateral margins of the segment 

 and meet the central one at the posterior extremity. 



(6) The antennules of both species are small, with a flagellum of ten or eight joints; 

 the antennae are nearly twice as long, with short flagella. 



(7) The maxillipeds of both species agree in having the basipodite fused with the 

 lamella to a point beyond the attachment of the endopod, so that the latter appears to 

 spring from the centre of a plate-like structure. 



(8) The characters of the spines on the propodus of the second thoracic appendage 

 of the two species differ. In S. exigua only one variety of spine is found, whilst in 

 S. carinata two types are present, one of which is peculiar to the species. The propodus 

 in the aduh male of S. exigua is further characterized by the presence of long delicate 

 hairs on its outer border ; these are not found in S. carinata. 



The above description was written before receiving Nordenstam's paper (1933). It 

 agrees with that given by Nordenstam for S. exigua and his specific name has therefore 

 been used. Nordenstam's description is based on the female only: in the above de- 

 scription the male characteristics are also included. 



13. Serolis carinata, Lockington (Fig. 11). 



S. carinata, Lockington, 1877, pt. i, p. 36; Richardson, 1899, p. 842; Richardson, 1900, p. 224; 

 Richardson, 1905, p. 321, figs. 353, 354. 



I have been able to examine specimens of both sexes of this species through the 

 generosity of Dr Waldo Schmitt of the United States National Museum, Washington, 

 to whom I wish to express my gratitude. Neither the description nor the figures given 



