Description of Female
Length, 24 mm.; depth, 4 mm.; width, 7 mm. Transparent in formalin. Ovigerous. First pleon segment only slightly shorter than last peraeon segment; head as deep as 1st 6 peraeon segments are long; 3rd peraeopod much the longest; 7th peraeon segment nearly equal to 4th, 5th and 6th; 1st 2 peraeon segments much deeper than rest. Ocelli somewhat localised dorsally and ventrally on head.
Antennae. First: Length 1 mm. Of 2 segments, 1st ovate with a few small setose spines; 2nd nearly 3 times as long, fringed with long flaccid sensory setae inferiorly. Second: Absent.
Mouthparts. Lower Lip: Inner lobes practically absent. Outer lobes and long connecting bar finely bristled. First Maxillae: Outer plate much longer than inner, outer margin finely toothed, inner margin with small setae, a stout end tooth. Inner plate ovate, tending to spoon-shaped, both margins with strong incised teeth, inner with a strong tract of fine bristles; tract of fine setae at base on outer margin. Second Maxillae: Outer plate barely longer than inner, both distally and marginally setose; a 3rd and median small distally setose lobe extending ½ along inner lobe. Mandibles: Cutting edge of 1 or 2 distal teeth; molar process strong, plate-like, with strongly toothed and bristled surface; a short tract of strong fine seta-like teeth on outer mandible margin. Maxilliped: Outer plates long, narrow, subtriangular; inner margins with strong teeth and a few setae; distal outer surface minutely toothed. Median plate subtriangular, reaching about ⅓ along outer plates.
Gnathopods. First: Basos slender, width less than ¼ length. Ischium more than ¼ basos, 2 or 3 setae posteriorly. Merus as long as ischium, anterior margin mostly oblique, contiguous with carpus proximal margin; free distal margin and distal ½ of posterior margin toothed; posterodistal angle right-angled, with setae; convex carpus anterior margin ½ basos length, with a few setae; posterior surface distally produced as triangular lobe about ½ along propod, posterior margin
Text-fig. 12.—Phronima sedentaria. (Forsk.). 195—Adult female. 196—Head of ♂, length 9 mm. 197—Pleon segments, ♂. 198—Antenna 1, ♂. 199—Antenna 2, ♂. 200—Gnathopod 1. ♂. 201—Gnathopod 1, ♂, dactylos. 202—Gnathopod 1, ♀. 203—Gnathopod 2, ♂. 204—Gnathopod 2, ♀. 205—Peraeopod 1, ♂. 206—Peraeopod 1, ♀, 207—Peraeopod 1, ♀, dactylos. 208—Peraeopod 5, ♂. 209—Pleopod coupling spines, 210—Epimeral plates, ♂. 211—Epimeral plates, ♀. 212—Telson, ♀,
slightly concave and finely toothed; end margin with strong teeth, acute posterodistal angle; free distal margin convex, tending to sigmoid; carpus greatest width ½ length anterior margin. Propod slender, slightly shorter than carpus anterior margin, about ¼ length, narrowing to dactylos; anterior margin has several setae, posterior margin toothed, surface has tracts of minute teeth. Stubby dactylos less than ⅓ propod length, apparently distally bifurcate. Second: Basos width ⅕ length, linear. Ischium nearly ¼ basos length, posterior margin has a few setae. Merus and carpus as before but comparatively longer and narrower; merus posterodistal angle less than 90°; total merus length nearly ⅓ basos. Carpus greatest width ⅖ length anterior margin; anterior margin slightly longer than ½ basos; posterodistal angle not reaching ½ along propod. Propod barely shorter than carpus anterior margin, greatest width about ⅙ length; anterior margin with setae, surface minutely toothed, posterior margin toothed. Dactylos about ⅕ length, partially surrounded by spoon-like sheath with fimbriated margins.
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Peraeopods. First: Basos width about ⅕ length. Ischium less than ¼ basos; posterior margin and surface with a few setae. Merus about ⅖ basos length, width ⅖ length, anterior margin convex, posterior straight, minutely toothed; margins and surface with a few fine setae. Carpus ⅔ surface, with scattered fine setae; posterior margin has fine comb of short teeth. Propod slender, somewhat dactylos-like, 4/5 basos length, tapering to 2 short strong spines; posterior margin finely toothed; margins and surface with scattered setae; surface has median tract of minute teeth. Third: Chelate. Basos greatest width between ⅓ and ¼ length; posterodistally produced to short narrow spur-like process, scattered fine marginal setae. Ischium globose, greatest length slightly more than ¼ basos; antero-distal angle produced downwards in short thumb. Merus globose, with narrow proximal neck, posterior margin more strongly convex than anterior, greatest width ½ length, length more than ⅖ basos. Carpus greatly expanded, ovate, short slender neck proximally, expanded so greatest width distally is subequal with merus length; anterior margin proximally almost straight, posterior margin convex; anterodistally produced to long finger increasing length ½ as much again so total length subequal with basos; end margin forming concave palm with smaller median tooth regularly fringed with single setae. Propod closing against palm and reaching well past long finger, inner margin has median tooth fringed with setae, total propod length ¾ basos; terminally a short spine-like dactylos. A few scattered setae on all segments but most numerous on carpal processes and propod. Fourth: Ischium ⅙ basos length; merus ¼ basos, carpus more than ½ basos; propod ⅓ basos; otherwise like 5th. Fifth: Width of basos about ⅛ length; anterodistal angle produced as short spur. Ischium total length about 1/12 basos; anterior margin produced a little as squarish flange with distinct angles. Merus ⅛ basos length, subrectangular, width ½ length, anteroproximal angle produced a little, acute. Carpus as wide, length ¼ basos, subrectangular Propod ⅕ basos length, width ⅙ length, tapering. Dactylos minute, spine-like, with sheath.
Pleopods. Normal. Rami and peduncle subequal.
Epimeral Plates. Shallow, ventral margins somewhat sigmoid, posterodistal angles produced as long, slender, backwardly directed processes, posterior margin concave.
Uropods. Long, slender, peduncles much longer than rami; tips of rami of 1st reaching as far as those of 3rd; 2nd with tips reaching to end of peduncle of
1st. Rami lanceolate, outer margins smooth, inner margins of outer rami and outer margins of inner rami convex, finely pectinate. First: Peduncle, rami in ratio 13:6. Second: Peduncle, rami in ratio 2:1. Third: Peduncle, rami in ratio 11:5. Telson: Small, regularly convex, barely reaching past base of uropod 3 peduncle.