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Description of Male
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Eyes very small, apart, about 1/3 width of head Body length, 5 mm; depth, 2 mm.; width, 1 1/4 mm.
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Antennae. First: Length, 1 1/2 mm.; nearly as long as 2nd. Flagellum of 11 segments, as long as peduncle, segments longer than wide, tufts of setae distally. Peduncle, 3rd segment 3/4 length of 2nd; 2nd 2/3 length of 1st; all with a few setae distally. Second: Length, 2 mm. Flagellum of 10 segments (9 m female), segments as above. Peduncle, 3rd segment 2/3 length 4th; 4th 2/3 length of 5th; all with a few setae distally, 3rd with 2 stout spines on inferodistal angle; 5th with a few pairs of marginal setae.
Mouthparts. First Maxilla Inner plate reaching palp site on outer; outer without palp but margin notched as though palp broken off. Maxilliped: Inner plate slightly shorter than outer; subrectangular, 3 stout teeth distally, 4 scabrous setae on rounded outer angle, 2 or 3 between or below teeth, about 4 down cleft Outer plate reaching 1/2 along carpus, narrow, outer margin convex, double row of long setae terminally and down inner margin to merus level. Basos, ischium, merus and carpus with 1 or 2 long spines on outer distal angle Merus, distal margin concave, convex outer margin more than twice length inner; 3 strong setae on inner distal angle. Carpus large, as wide as inner margin is long, inner margin 3/4 length merus outer margin and 2/3 inner merus margin, carpus inner margin produced as strong flange, double row of long setae on distal 2/3 and angle. Propod width 2/3 length, as long as carpus outer margin, distal angles with strong tufts of setae, 5 or so strong fine-combed spines across dactylos base. Small conical dactylos 1/3 propod length, long seta on outer margin; 1 to 3 strong terminal setae, usually one, with 3 smaller setae immediately below.
Gnathopods. First: Sideplate deeper than wide, subrectangular, ventral angles rounded, ventral margin convex and spined, triangular process not obvious, not excavate posteriorly. Basos very narrow proximally, width 1/4 length, a few long setae posteriorly, single seta on anterodistal angle and on posterodistal angle of subrectangular ischium, ischium less than 1/3 basos length Merus basically subrectangular, as large as ischium, anterior margin and proximal 1/2 of carpus posterior margin contiguous; posterior margin rounding to distal angle with
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Text-fig. 1—Chiltonia mihiwaka (Chilton) 1—Antenna 1. ♂ 2—Antenna 2, ♂. 3—Maxilla 1 4—Maxilliped 5—Maxilliped palp. 6—Gnathopod 1, ♂. 7—Gnathopod 1, ♂, palm and dactylos. 8—Gnathopod 1, ♀. 9—Gnathopod 2, ♂ 10—Gnathopod 2, ♀ 11—Peraeopod 2, sideplate. ♂. 12—Peraeopod 5. ♂ 13—Pleopod 2, ♂. 14—Pleopod 2, plumose seta from ramus 15—Pleopod 1, ♂. 16—Pleopod 1, tip of inner ramus, ♂. 17—Uropod 1., 18—Uropod 2. 19—Uropod 3. 20—Telson,
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Text-fig. 2.—Chiltonia mihiwaka (Chilton). Male. 1—Peraeopod 1. 2—Peraeopod 3. 3—Peraeopod 4. 4—Epimeral plates. Chiltonia rivertonensis, n.sp. Male. 5—Gnathopod 1. 6—Gnathopod 2. 7—Peraeopod 1. 8—Peraeopod 1, posterior margin of carpus, 9—Peraeopod 4. 10—Peraeopod 5, 11—Pleopod 1. 12—Uropod 3. 13—Telson.
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several strong setae. Subtriangular carpus 3/4 basos length, anterodistal angle produced as slight spur with strong tuft of long setae; posterior free margin more or less straight with row of about 15 increasingly longer fine-combed setae. Propod subrectangular, 2/3 basos length; single seta medially on anterior margin, group on distal angle; posterior margin with long setae medrally, several near distal angle; posterodistal angle produced as small thumb-like lobe with seta and strong spine; palm transverse, with a few small setae; numerous long setae on surface below palm; curved dactylos as long as propod is wide, impinging on palm below distal lobe and against small stout spine at lobe base. Second: Sideplate subrectangular, angles rounded, ventrally spined, depth nearly twice width, without triangular process or posterior excavation. Basos and ischium as in Gn 1; merus as long as ischium, L-shaped, about 3 small setae on rounded posterodistal angle; anterior margin contiguous with proximal margin of subequal subrectangular naked carpus. Propod large, subrectangular, attached to carpus by small stalk anteroproximally, anterior margin as long as basos, slightly shorter posterior rounding to convex proximal margin which is mostly free; palm transverse, slightly convex, with small distally produced lobe Curved dactylos as long as propod is wide, suggestion of small lobe on inner margin near dactylos base.
Peraeopods. First: Sideplate subrectangular, angles rounded, ventrally convex and spined; depth twice width, triangular process absent not excavate. Basos slightly shorter than sideplate depth, several long setae posteriorly, width 1/4 length. Ischium as long as basos is wide, subrectangular, posterodistally spined. Merus piriform, length more than twice width, 3/4 basos length, single group of setae mid-anteriorly, strong group on downwardly produced distal angle; 4 strong setae-tufts on posterior margin, spines on distal angle. Carpus narrower, slightly shorter, tuft of setae on anterodistal angle, 4 tufts on posterior margin, angle spined. Propod as long as merus, width 1/3 length, setae on anterodistal angle, 7 single or paired spines on posterior margin Curved dactylos 1/3 propod length, seta on inner margin Second Sideplate deeply excavated, L-shaped, ventral margin spined, rounding broadly to distal margin; otherwise as Pr. 1. Third: Anterior sideplate lobe smaller than posterior; strong convex posterior margin of latter serrate, minutely spined. Basos ovate, slightly longer than wide, single short spine proximally on anterior margin, 6 or so on distal 1/2, group on angle, convex posterior margin serrate and minutely spined. Ischium subrectangular, 1/4 basos length, anterodistal angle spined Merus piriform, 3 groups of 1 or more stout spines on serrate margins, slightly produced downwards posterodistally; posterior margin 1/2 basos length, width 1/2 length. Carpus narrower, as long as merus posterior margin; 3 groups of strong spines on anterior margin, small seta mid-posteriorly, angles strongly spined. Propod as long as carpus, width 1/4 length, 6 single or paired spines anteriorly, seta mid-posteriorly, tuft on angle. Fourth: Two pairs of small spines on carpus posteriorly; propod anteriorly with 5 spine groups; otherwise like Pr. 3. Fifth: Basos anterior margin with tuft of long setae proximally, 7 strong single spines on anterior margin, anterodistal angle strongly spined; as wide as anterior margin is long; posterior margin greatly convex, serrate and minutely spined Propod anterior margin with 4 spine-groups; otherwise like Pr. 4.
Epimeral Plates. First Subtriangular, anterior margin straight, posterior slightly convex with about 3 minute spines and serrations, angle acute. Second
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and Third: Subrectangular tending to trapezoid, angles sharp, posterior with 5 or 6 minute spines.
Pleopods. Biramous, rami longer than peduncle, inner shorter than outer, 2 coupling spines; outer ramus of about 10–12 segments, each with plumose setae, inner with about 6 segments. Plumose setae of all pleopods peculiar in being apparently solid halfway along for short distance with different refractive index. Male first pleopod with inner ramus terminally modified to long backwardly and outwardly bent whip-like lash. This was not observed in female.
Uropods First: Rami as long as peduncle, outer with 2 or 3 stout dorsal spines, inner with 4 or 5, about 4 terminal spines on each; peduncle with 5 dorsal spines on inner margin, one on outer. Second: Peduncle as long as rami, about 5 strong dorsal spines distally. Inner ramus with 5 dorsal and 3 terminal stout spines; outer with 2 dorsal and 4 terminal. Third: One segment, somewhat taperingly globular, about 3 long terminal setae and a stout short spine; on upper margin medially 1, then 3 or 4 strong setae; 3 or 4 smaller setae on surface. At least one specimen shows marked suture across one uropod posterior to the medial group of spines, although it is not obvious on the other uropod of pair; this suture, if present, is masked in the type slides by the osmic acid preparation. Telson: Subrectangular, distal angles rounded, appears cleft at most for about 1/4 length.