PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 109(2):353-365. 1996. Pholidichthys unguis, a new species of pholidichthyid fish from Northern Territory and Western AustraUa Victor G. Springer and Helen K. Larson (VGS) Division of Fishes, National Museum of Natural History, Washington, D.C. 20560, U.S.A; (HKL) Museum and Art Gallery of the Northern Territory, GPO Box 4646, Darwin NT 0801, Australia Abstract. — Pholidichthys anguis is only the second species known in the family Pholidichthyidae. It differs from P. leucotaenia in having 87-98 dorsal-fin rays (vs. 66-79), 70-81 anal-fin rays (vs. 49-62), 90-101 total vertebrae (vs. 71-79), a more slender body, and a shorter head and maxillary. In addition, the color pattern of juveniles (—50-103 mm SL) differ in having the depth of the slender dark stripe on midside at vertical from anal-fin origin about 1 mm, usually much less (vs. depth 2.5-3.3 mm). Study of whole specimens and skeletal preparations of P. anguis indicates that the species exhibits the same familial specializations as P. leucotaenia. The two species are distributed al-lopatrically. We hypothesize that the common ancestor of the two species of Pholidichthys had a Tethyan distribution exclusive of Australia-New Guinea (ANG). When ANG collided with SE Asia, the ancestor invaded ANG. During a subsequent interglacial period, ecological factors contributed to the isolation of the Australian portion of the ancestral population from the New Guinea portion, and permitted divergence of the isolates. Pholidichthys and its only included spe-cies, P. leucotaenia, sole representative of the Pholidichthyidae, were described by Bleeker (1856) from Boeroe (= Buru), In-donesia. A purported second species, P. an-guilliformis, was described by Lockington (1882) from the Gulf of California. The ho-lotype of P. anguilliformis has not been seen since its description, but characters given for the species (especially its all spi-nous dorsal fin) and its type locality, prob-ably indicate that it is not congeneric or confamilial with Pholidichthys Bleeker. Larson {in Trnski et al. 1989) indicated that an undescribed species of Pholidichthys (whose description is the main purpose of the present paper) also exists in the Indo-Pacific. Her report was based on specimens brought to her attention by prawn research-ers of the Northern Territory Fisheries Di-vision, Darwin. We know of no other de-scribed or undescribed taxa that are refer-able to the Pholidichthyidae. In the last major study of Pholidichthys, Springer & Freihofer (1976) reviewed the literature on P. leucotaenia and described aspects of its osteology, neurology, and on-togenetic color-pattern changes. They also remarked on its behavior in aquaria, plotted its geographic distribution, and discussed its possible familial interrelationships. Materials and Methods Specimens of the new species are listed in the description. All but one specimen, an adult female, 245 mm SL, which we des-ignate holotype, are small juveniles (most less than 70 mm SL, none between 103 mm and 245 mm) obtained from trawl hauls. Most of the specimens are curled and twist-ed and do not permit accurate SL measure-
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