1890.] or XUE GENUS SBBGESTES. 965 



S. penerinJci, Bate. — The specimen represented by Bate (p. 418, 

 pi. Ixxvi. fig. 3) is rather young, 8 mm. long. I have examined a 

 number of specimens, between 6'4 and 14 mm. in length, partly 

 from the Plankton expedition and partly from our museum. 

 Specimens from c. 7'5 mm. to 14 mm. in length are easily distin- 

 guished from those of the same length oE S. vigilajc, Stimps., by 

 having the third, fourth, and fifth abdominal segments — in the 

 younger specimens also the sixth segment — dorsally armed with 

 spines, which in larger specimens are shorter than in the stage 

 figured by Bate, but yet well developed ; the spine on the third 

 segment is almost perpendicular. lu older specimens the eye- 

 stalks are somevvliat shorter than in S. vigilax, Stimps., but yet 

 long. In the older stages the rostrum is much shorter than in 

 Bate's figure, but yet longer than in S. vigilaw, and its distal part 

 is slender and directed horizontally forwards; in the younger 

 stages it is tow-ards 4 or more of the length of the eye-stalks and 

 recalls somewhat that in S. incertus, m. (see below), but in 

 specimens that have attained the length of 8 mm. it is destitute 

 of a dorsal spine. In specimens c. G'4 mm. long the rostrum is 

 about half as long as the eye-stalks, with a very short dorsal spine 

 a little way from its base. In the antenn. ped. the third joint is 

 scarcely longer than the first. (In the young specimens the 

 anterior abdominal segments are ventrally armed as described by 

 Bate.) On the ext. br. of urp. the length of the ciliated part 

 varies, as in S. vic/ila,v, in accordance with the length of tiie 

 specimens, occupying from | to 4 of the exterior margin ; a tooth 

 is present in the younger, not in the old specimens. The adult 

 form is described above, bearing the same name. 



S. incertus, m., is Ihe Mastir/ojms of the adult described above. 

 I have seen rather numerous specimens from 6'2 to 13 ram. in 

 length. They are more slender than the corresponding stages of 

 S. penerinhi, Bate, which they closely agree with in the antenn. 

 ped., the length of the eye-stalks, and the dorsal armature on the 

 abdominal segments. But they are easily distinguished from this 

 species by the ext. br. of urp., on which the ciliated part in all 

 specimens occupies scarcely | of the exterior margin, and the spine 

 is rather long. Moreover, the rostrum, which in proportion to 

 the length of the animal is from more than the half to scarcely ^ 

 of the length of the eye-stalks, is rather characteristic : seen from 

 the side the basal part is rather short and directed obliquely 

 forwards and upwards, and then it suddenly becomes produced 

 into a slender and distally very fine spine much longer than the 

 basal part and quite horizontal ; at the distal end of the basal part 

 the ujjper margin is armed with ajine spine, which is very short in 

 the older specimens, and just heyond tuhich the margin is somewhat 

 concave in outline. In the young specimens the first two abdominal 

 segments are ventrally in the median line armed with a lobe 

 produced to a spine, and in these and even in specimens c. 10 mm. 

 long the posterior margin of the carapace is armed with an erect 

 spine. 



