Tharyx Webster and Benedict 1887

Genus Tharyx Webster and Benedict, 1887

Type species: Tharyx acutus Webster & Benedict, 1887, by monotypy.

Diagnosis. Prostomium conical; peristomium elongate, with pair of grooved dorsal tentacles arising on posterior margin anterior to setiger 1; first pair of branchiae typically arising immediately posterior to dorsal tentacles either on posterior margin of peristomium or on setiger 1; abdominal segments sometimes beadlike. Noto- and neurosetae arising close to one another, not widely separated. Setae include simple capillaries in anterior and middle setigers, acicular spines in posterior setigers with irregular notched tips, sometimes appearing more or less bidentate, with pair of stunted or rounded knobs but never with distinct, sharply pointed teeth; spines present either in both posterior noto- and neuropodia or only in neuropodia. Pygidium with terminal anus and small ventral lobe or disk.

Remarks. Blake (1991) determined that the type species of Tharyx, T. acutus Webster & Benedict, 1887 had knob-tipped acicular spines in addition to capillaries. At the time, Tharyx species were defined as having only capillaries (Hartman 1961). Blake (1991) limited Tharyx to those species having knob-tipped spines and moved species having only simple or serrated capillaries to the genera Aphelochaeta Blake, 1991 and Monticellina Laubier, 1961 respectively. The genus Tharyx superficially appears most closely related to Caulleriella in that both genera have species with modified spines that are more or less bidentate. Caulleriella and Tharyx are easily distinguished, however, by the position of the noto- and neuropodia. In Caulleriella, the setal fascicles are widely separated from one another, so much so that in cross section of some species, they appear to be positioned at four corners. In Tharyx, on the other hand, the setal fascicles are close together.

Two new species of T haryx are described as part of this study. One species from Alaska had been previously referred to the genus Chaetozone. The second species, from the Puget Sound, Washington, was known in Puget Sound monitoring programs under a provisional Tharyx designation.