Systematic Position

As the two distal segments of the 5th pereiopods are setose on both margins and organs of Pesta are present, the specimen belongs to either the "S. corniculum" or the "S. sargassi" groups of the subgenus Sergestes s.s. The absence of both 3rd maxillipeds in the only specimen available, does not allow it to be placed in one of these two groups, as the relative length of this appendage is apparently the only feature distinguishing one group from the other (see Burkenroad, 1937a: 320). However, owing to the great similarity in appearance between this specimen and the illustrations of S. corniculum, especially as regards the ridges, grooves and shape of the carapace, I believe it to be closely related to that species. Assuming it to belong to the "S. corniculum" group, the absence of a supraorbital spine distinguishes it from S. corniculum, S. disjunctus and apparently from the inadequately described S. nipponensis; the presence of a transverse groove between the hepatic spine and the lateral ridge anterior to it distinguishes it from S. rubroguttatus and S. coalitus; while the low ocular tubercle distinguishes it from S. erectus. This leaves only S. seminudus to be considered. This species described from Indonesian waters by Hansen (1919), is very similar indeed to the New Zealand specimen, differing only to a small extent in the relative lengths of the segments of the antennular peduncle. However, our female specimen cannot be definitely identified with S. seminudus (if. indeed, it belongs to the "S. corniculum" group) until mature males arc taken and the petasma compared to that of Hansen's species.

It should be noted here that Burkenroad (quoted by Gurney and Lebour, 1940: 38) states that there are three species in the Atlantic confused with S. corniculum "but he is not at present able to give a final opinion or names for the species which he has distinguished". In the same year Burkenroad (1940) described five new species belonging to the S. corniculum and the S. sargassi groups, by comparing them, without illustrations, to one another and to S. seminudus, S. henseni and S. "sargassi Ortmann" of Hansen. This does not allow us to know what he means by these species. Until his promised revision of the genus (1937a, 1940, 1945) is published, it is very difficult, if not impossible, to identify many species which he has dealt with in a preliminary manner.