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Deep-Water Crustacea of the Genus Sergestes (Decapoda, Natantia) from Cook Strait, New Zealand

Extended Diagnosis

Extended Diagnosis

The single female specimen available has the cephalothorax separated from the abdomen and both 3rd maxillipeds and certain pereiopods missing. A short description of the main characters of this damaged specimen is given below.

A relatively large, attenuated, firm-bodied shrimp with long appendages and prominently ridged carapace.

Rostrum relatively small, compressed, very slightly raised above the anterodorsal mid-line of the carapace and hardly projecting beyond the anterolateral margin of the carapace. Anterior margin of the rostrum with an acute tip flanked dorsally and ventrally with short concave portions. Carapace relatively long and attenuated, greatest depth, at posterior margin, a little less than two-fifths the length. Supraorbital crest prominent, but supraorbital spine absent. Hepatic spine small but distinct. Cervical groove well defined dorsally and laterally, almost continuous anteriorly with a well defined lateral ridge running from anterior to the hepatic spine towards the base of the antenna. Suprabranchial groove and ridge prominent with a slightly less prominent horizontal ridge laterally across the branchial region.

Telson weakly grooved dorsally, distally setose with no dorsal spinules present.

Eyes not large, cornea considerably shorter but broader than distal segment of ocular peduncle. Ocular tubercle present, broader than high.

Antennular peduncle relatively narrow and attenuated, proximal segment a little longer than the third, which is itself longer than the second. Antennal scaphocerite, with outer margin distinctly convex, reaches a little beyond the proximal third of the third segment.

Mouth parts as for genus. As both 3rd maxillipeds are missing, it is impossible on this feature to be sure of the group to which this specimen belongs.

The 1st pereiopod reaches a little beyond the distal end of the antennular peduncle and is non-chelate. 2nd and 3rd pereiopods extend well beyond the antennular peduncle, and both bear minute chelae of the type apparently characteristic of the "S. corniculum" and the "S. sargassi" groups (see Burkenroad, 1937a: 320). Here the fixed finger is shorter than the free finger, both bearing distally a fan of setae, while the fixed finger and a portion of the hand bear a conspicuous longitudinal series of very long plumed setae exactly as shown by Hansen (1922, Pl. VII, figs. g–h). The ischia of 1st and 2nd pereiopods bear a spine disto-laterally. The 4th and 5th pereiopods are both of the compressed laminar type usual in the genus, the 4th reaching to the distal end of the antennal peduncle, while the 5th, with both margins of the two distal segments setose, reaches a little beyond the distal half of the merus of the 4th.

Setose portion of external margin of uropodal exopodite half as long again as non-setose portion. No tooth present on this outer margin.

Female with no teeth or lobes medially on coxa of 3rd pereiopod, but with a small spinule posterodistal to the opening of oviduct.

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