Total length (excluding setation) up to 0.59 in (15 mm) (average total length 0.38 in [9.8 mm]). Carapace length of mature female is up to 0.26 in (6.8 mm), approximately 1.5 times longer than deep, unsculptured, with usual posterodorsal indentation. Rostrum long, clearly extending beyond eye, distally rounded, length approximately 2.7 times width; with ventral projection or "keel" more or less rectangular, unpaired, but with slight medial depression gently sloping upward toward ventral surface of rostrum and with slightly protruding, blunt anterolateral corners. Compound eye is large, well developed; pigmented (visual surface), extensive, covering at least distal half. Telson short, approximately as long as wide, rectangular, or with sides slightly diverging posteriorly. Caudal furcae elongate, approximately twice length of telson, and sometimes greater than twice its length;; acute spines along posterior dorsal borders of pleonites. Males have second antenna that is curved rather sharply in an anterior direction, but considerable variation exists (from extending almost directly anteriorly up to appearing slightly cork-screwed).
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