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(Rathbun, 1914)

The carapace is much flattened, not granulate, but very minutely punctate. The various regions are not well defined, but some, viz. mesogastric, cardiac, intestinal and inner branchial regions, are inflated, while others (epigastric and hepatic regions) are slightly depressed. The only deep sulcus is the nearly semicircular cervical groove, situated behind the middle of the carapace, shallower in its median part; from either end parts backward a very short groove, concave outward, and another yet shorter groove runs transversely. The branchial regions are scarcely defined from the obtusely-triangular intestinal area, and laterally they are strongly declivous towards the bases of the second to fourth ambulatory legs; the sloping portions are defined superiorly by a sharp line, somewhat curved anteriorly and nearly continued till the margin of the carapace. There are two pairs of very indistinct transverse depressions, one on the level of the cervical groove and one running inward at the level of the posterior lateral teeth. The epigastric lobes are present, but very indistinct, and anteriorly to these the front is perfectly flat, laminar and horizontal, with a straight anterior margin, that passes with obtuse angles into the lateral margins. The upper orbital margin is strongly S-shaped and separated from the lateral margin of the front by a closed incision, beginning with a triangular sinus. The distance between the external orbital angles is less than the length of the carapace; the angles are prominent, but obtuse at tip, and their lateral margins are markedly diverging backward; the epibranchial teeth are acute, with the lateral margins subparallel, and separated by deep sinuses; the anterior pair of these teeth is larger and more depressed than the posterior pair; distance between tips of posterior pair of teeth is equal to length of carapace. Postero-lateral margins slightly converging backward; posterior margin nearly equal to anterior breadth of front. The front projects a considerable way beyond the bases of the antennules, that are quite concealed in dorsal view, and the bases of which are separated by a triangular “ nasal lobe ”. The epistome is narrow, 6 1/2 times as broad as long, excavated, and the posterior margin, between the ridges of the endostome, is somewhat crenulate. The antennae fill the gap between the front and the blunt inner orbital lobe. Pterygostomial regions granular and somewhat hairy; a granulated ridge runs obliquely backward from the anterior angles of the buccal cavern, disappearing distally. In the male the breadth of the exognath of the external maxillipeds measures, according to Miss Rathbun, 1 3/5 times the width of the ischium; in my specimen this exognath is 1 2/5 times as broad as the ischium and is much swollen, smooth and entirely glabrous, as is usual in the male of this genus, reaching nearly as far forward as the large auricle of the merus; outer surface of both ischium (the lateral margins of which are subparallel) and merus likewise hairless. In the female the exognath is flattened; it reaches as far forward as in the male, but it is much narrower, not attaining even the width of the rather broad ischium; the outer surface of the whole maxilliped is covered with very short hairs.
The abdomen of the male is of the usual shape, with the lateral margins slightly converging forward, the terminal segment being narrow, longer than broad at the base, and the penultimate segment shorter and three-fourths of the width at the base. The eggs of the female are very small and most numerous.
The chelipeds of the male are equal in size, very stout and bulky. The edges of the meropodite are somewhat roughened by granules; upper and inner margins provided with some hairs; there is, besides, a small patch of hairs on the inner surface; the upper margin has no subdistal projection. The wrist is globular, with some very minute transverse granulated rows on the upper surface; the inner surface is flattened, bordered above and below by a granulated row and ending anteriorly into a rather long, triangular, depressed spine, with the tip acuminate. The chela is as long as the anterior margin of the front; the palm is smooth, but covered with very minute granules when examined under some magnification, shorter than the fingers; the granules are arranged in some oblique rows near the carpal joint, and the upper margin is elevated into a depressed lobe, which occupies, as Miss Rathbun remarks, the proximal two-thirds of the margin; the outer surface of the palm is somewhat prominent near the carpal joint; a very indistinct horizontal line runs from the carpal joint to the tip of the fixed finger, and a trace of a second (oblique) line is visible above it on the palm; the fingers are very high at the base, largely compressed, very slightly spooned at the tip; the back of the mobile finger is covered with minute granules, and the cutting margin is provided with about 13 obtuse teeth, that are largest in the middle; that of the fixed finger has proximally 6 teeth, increasing gradually in size, so that the two terminal ones are very large, then follow two small teeth and at last a much larger tooth at the beginning of the horny extremity of the finger.
Ambulatory legs long and slender, the penultimate pair being 1 1/2 times the maximum breadth of the carapace. Meropodites about 3 1/2 times as long as broad, with a sharp subdistal tooth at the anterior margin, except in the case of the terminal pair of legs; both anterior and posterior margins with short hairs, intermingled with longer hairs; above the bases of the legs clusters of club-shaped hairs are observed. Carpo- and propodite together are as long as the meropodite; both margins are fringed with hairs, especially at the hind margin of the much flattened propodite, that is paddle-shaped, and longitudinally-oval in the posterior legs. Dactyli falciform, depressed, as long as the hind margin of the preceeding joints, and likewise fringed. (Tesch, 1918a)

Type locality: Point Jamelo, Luzon, Philippines.
Range: Nias (Tesch, 1918a); Japan - Ishigaki-jima (Minei, 1972, Miyake, 1983), Kinokawa, Wakayama (Nomoto et al., 1999); Philippines - Luzon (Rathbun, 1914a); Indonesia - Ambon (Serène & Moosa, 1971).

Ptychognathus altimanus