136 CRUSTACKANS OF THE 



one of the female specimens the lateral grooves dividing 

 the postfrontal lobes from one another are wanting, the 

 internal lobes being coalesceut with the external ones, 

 but this is of course an abnormity. The orbits are large 

 as in Ses. angustifrons and the eye-peduncles project a 

 little more beyond them than in the species from Tahiti. 



Both species may at first sight be distinguished by the 

 different shape of the extraorbital tooth. In 

 Ses. Amphinome (Fig. 16«) this tooth is less prominent, 

 less acute and comparatively much smaller 

 than in Ses. angustifrons, its outer margin is more curved 

 iuward and the notch separating it from the epibranchial 

 tooth is larger and deeper. In the species from Ta- 

 hiti only a trace of a second epibranchial tooth is ob- 

 served, but in Ses. Amphinome this second tooth is quite 

 distinct though small and little prominent, and separated 

 from the first by a distinct notch ; both epibranchial teeth 

 project laterally less outwards than the extra-orbital tooth 

 and are obtuse. In Ses. angustifrons the extra-orbital tooth 

 is slightly longer than the epibranchial, but in Ses. Am- 

 phinome the first epibranchial tooth appears distinctly 

 somewhat larger and longer than the extra-orbital; 

 the outer margin of the first epibranchial tooth is slightly 

 arcuate and this tooth is somewhat raised upwards. A few 

 short fine hairs are seen on the postfrontal lobes, on the 

 tubercles of the hepatic area and on the lateral margins 

 of the epibranchial teeth. 



As regards the lower surface of the cephalothorax, e. g. 

 the form of the epistome and of the outer maxillipedes, 

 the two species closely resemble one another; in both the 

 merus-joint of the latter is little longer than broad, the 

 proportion being as 6 : 5, it is oval and rounded anteriorly. 



The abdomen of the male (Fig. 16<") has also about the 

 same form, but the penultimate segment is a little 

 shorter in proportion to its breadth: in the male of 

 Ses. angustifrons the penultimate segment is 2^/3 mm. long, 

 its posterior margin 5^/- mm. broad. 



Notes from the Leyden Mwseum , "Vol. XXI. 



