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



This description is mainly based on a male specimen, with carapace length 23 mm, collected by the Pawley brothers in 1941.

A large, deep-bodied, heavily-built shrimp with relatively soft integument and prominent eyes.

Rostrum relatively large, compressed, directed obliquely dorsally; anterior margin produced in its centre into a short acute point and with a small acute tooth, sometimes rudimentary, on anterodorsal margin. Carapace deep, greatest depth, across branchial region, just under half greatest length. Supraorbital and hepatic spines absent. Cervical groove weakly defined laterally, not continuous dorsally; posterior cervical groove apparently absent; supra branchial groove and ridge weak.

The 6th abdominal segment, which is longer than the telson, ends posteriorly with a minute dorsal spinule. The telson is acute distally and dorsally grooved with three pairs of minute spinules on the distal portion of the dorsal surface.

Eye with cornea large, considerably wider and also longer than distal segment of ocular peduncle. No ocular tubercle present.

Antennular peduncle relatively short and stout, proximal segment not as long as second and third together, third a little shorter than second and twice its own depth. Antennal scaphocerite reaches almost to centre of this third peduncular segment.

Mouthparts as for genus. The 3rd maxilliped is relatively long and slender, but shorter than the 2nd or 3rd pereiopods; it extends a little beyond the distal end of the antennular peduncle. The dactylus is divided into six and the propodus into two subsegments.

The 1st pereiopod reaches to about the middle of the propodus of the 3rd maxilliped and is non-chelate. The 2nd and 3rd pereiopods both reach well beyond the antennular peduncle and are both minutely chelate. The 4th and 5th pereiopods are both of the compressed laminar type usual in the genus.

Non-setose portion of external margin of uropodal exopodite twice length of setose portion. Endopodite a little more than two-thirds length of exopodite.

Male with petasma as shown (Figs. 15, 16); processus ventral is wide at base with slender, unarmed tip, relatively short, not reaching as far as lobus armatus or terminalis. Lobus armatus long, subequal or longer than lobus terminalis, armed with 3 to 5 crochets distally and a number along the inner margin; well-defined lobus accessorius at base, armed with several crochets. Lobus terminalis and lobus connectens both armed distally and both produced proximally into an armed protrusion. The unarmed lobus inermis projects beyond the lobus terminalis and is subequal with the lobus connectens.

Female with posterior margin of 5th thoracic sternite convex and bulbous and coxa of 3rd pereiopod produced medially into two blunt lobes.