I896.J OF THE GENUS SEHGESTES. 959 



vii. Notes on the Species in Group II. 



A. S. henseni (Ortm.). — Of this interesting species I have seen 

 only two adult specimens, lent me by Geheimrath Prof. Dr. V. 

 Hensen. As the representation by Ortmami (p. 38, Taf. iii. fig. 3) 

 is rather deficient, I shall add some notes. The rostrum is low 

 and short; the supraorbital and hepatic spines are short. Mxp.' 

 is considerably longer than trl.' and its 4 proximal joints, though 

 more slender than in the following species, are yet much stouter 

 than in trl.' ; the 2 distal joints are quite naked along one margin, 

 the fifth almost more than double as long as the sixth, which is 

 divided into 5 subjoints, the last 4 of which are equal in length, 

 while the first of them is as long as the two following together ; at 

 the base of the first subjoint and at the apex of the first, third, and 

 fifth subjoints is found a long spine ; at the apex of the second, 

 fourth, and fifth subjoints a spine about half as long as the long 

 spines ; finally along the same margin a fine comb of very numerous 

 spines about as long as the diameter of the joints ; the fifth joint 

 of mxp.' has about 10 longer spines along the margin and on its 

 distal two-filths a comb similar to that on the sixth joint, but its 

 spines become shorter towards the base. By this singular armaturo 

 the species is easily distinguished from all other species known to 

 me. Above trl.° a large and a very small branchia, the latter of 

 which is less than a third as long and but half as broad as the large 

 branchia ; above trl.^ two branchia), the anterior somewhat larger, 

 the posterior somewhat smaller thau the small branchia above trl.^ ; 

 thus the branchiio are very different from those in the ocher species 

 of the group. In the following species we find a well-developed 

 process on the third joint of trl.' and a similar one on trl.^, but in 

 this species the process in trl.' is rudimentary and wanting in trl.' 

 On the ext. br. of urp. no spine is found on the exterior margin, 

 and in the one specimen the ciliated part occupies three-fifths, in 

 the other specimen almost four-fifths of its length. In no other 

 species have I met with any similar variation in this feature, but 

 it also exists in the larvae (see below). 



S. sargassi, Ortmaan (p. 34, Taf. iii. fig. 1), is the Mastiyopus 

 of S. hetiseni. As the material seen by me is rather incomplete, the 

 larger specimens being not very large and besides defective, I add 

 only a few remarks to Ortmann's description. Mxp.^ is elongat«d 

 and inerassated in proportion to the legs as in the adult, the fourth 

 joint at the apex and just above the articulation produced into a 

 large, conical pz'ocess— a very good character for the species ; and 

 in a larva a little more than half-grown the sixth joint was already 

 divided into the 5 subjoints. In the largest well-preserved speci- 

 men, 8 mm. long, I found above trl ."a large branchia and a lamella, 

 comparatively somewhat larger than usual, which had begun to 

 develop itself into a very small branchia, above trl.* a very small 

 branchia and a simple lamella; the normal lamella; above trl.' and 

 trl." are a little larger than usual. As in the adult the ciliated pari; 

 on the exterior margin of the ext. br. of urp. occupies about three- 

 fifths or four-fifths of its length in specimens between 4'5 mm. and 



Pboc. Zoor.. Soc— 1806, No. LXII. 62 



