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Discussion
This species is taken in wells in the Canterbury region. The specimen I have figured and described is from a 40-foot well, West Eyreton (the type locality), and is from the Chilton collection but taken some 39 years later than the type (May, 1921). None of Chilton's material seems to contain adult males or even recognisable juvenile males.
I recently received specimens from Mr. Baughan Wisely collected “where the Selwyn River crosses under the Christchurch-Southbridge railway line. At this point, which is readily accessible by road, the shingle is rounded and covered with a fine coating of algae; these specimens were found buried in this shingle down to a depth of 6 inches”
This is the first record, then, from a stretch of open water; Chilton's earlier records from such localities were later proved to have been P. helmsii or P. propinquus. I understand, however, that the Selwyn River passes underground, at least partially, in various places, and this may account for the occurrence of P. fragilis in open reaches. The specimens are typical of P. fragilis in having the eyes entirely absent.
Phreatogammarus propinquus Chilton, 1907. (Figs. 35–41.)
Chilton, 1907: 388, pl. xi, figs. 1–6.
Chilton, 1909a. 56 (in part).
Chilton, 1918: 84, figs. 2–4.
Length, 5 mm. Urosome segments with only 1 or 2 long slender setae dorsally.
Antennae. First: Longer than second; accessory flagellum of 4 segments. Peduncle, 3rd segment ½ length 2nd, narrower; 2nd ⅔ length 1st: each has a few setae distally. Flagellum about twice peduncle length, of about 20 segments, all longer than wide and with a few long bristles distally. Second Flagellum
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11-segmented, reaching at least ½ along 1st antenna flagellum; segments as above. Peduncle, 5th segment slightly shorter than 4th; 2nd as long as 3rd, ½ length 4th; gland-cone prominent; bristles on margins of all segments.
Mouthparts. Not dissected out and mostly obscured; only mandibular palp clear enough to figure. First segment small, a single (?) strong seta on distal margin; 2nd, inner margin convex, about 5 long strong setae on distal ½, more than twice length 1st, width ⅓ length; 3rd ¾ length 2nd; distally truncate; oblique truncate portion has 10 to 11 setae, end 3 or 4 long, remainder short.
Gnathopods First: Sideplates not dissected. Basos widening distally, greatest width ⅖ length; long setae on margins especially posterior. Ischium ⅖ basos length; strong fringe of long setae posterodistally. Merus subrectangular, width slightly less than length, length ¼ basos; posterodistal angle rounded, distal margin fringed with long setae. Carpus with nearly ½ length; length ¾ basos; convex anterior margin has 2 long single setae, about 3 at distal angle; posterior margin more or less straight, mostly fringed with long setae. Propod subtriangular, distal width slightly less than greatest length; length ½ basos; slightly convex anterior margin has about 2 pairs of long setae, a strong tuft on distal angle; posterior margin more or less straight, naked; transverse palm at right angles with posterior margin, but posterodistal angle rounded; palm has several long setae, about 5 short seta-tipped spines; row of 4 short setae posteriorly. Strong dactylos as long as palm, inner margin has a few bristles, 4 or 5 very oblique teeth. Second: Sideplate deeper than wide, lateral margins straight, rounding to convex ventral margin, a few long fine setae ventrally and posteriorly. Basos widening slightly distally, width ⅓ length, long setae on margins. Ischium ¼ basos length, about 3 long setae on posterodistal angle. Merus subrectangular, slightly longer than wide, slightly shorter than ischium, long setae on end margin. Carpus subtriangular, greatest width slightly more than length, length ⅖ basos; anterodistal margin slightly convex, sharp angle has 1 or 2 long setae; posterior free margin small, produced between merus and propod as small, rounded, strongly-setose lobe; setae on end margin. Propod subtriangular, almost basos length, greatest width proximally, ⅔ length; margins strongly convex proximally, straight for rest of length; anterodistal angle has tuft of long setae; a few setae anteriorly; posterior margin rounded proximal ¼ has 3 ranks of numerous long setae; palm defined only by presence of about 14 palmar spines singly or in pairs on remaining ¾ of margin, each spine has strong terminal seta; proximal 5 spines the strongest; long fine setae scattered on margin. Curved dactylos ¾ propod length, a few fine surface setae, 8 or 9 very oblique teeth on inner margin.
Peraeopods. First: Sideplate not easily distinguished. Basos constricted proximally, width ¼ length, both margins setose. Ischium subsquare, about ⅕ basos length, 2 or 3 setae posterodistally. Merus anterior margin slightly convex, has 3 strong single spines; width ⅓ length, length ⅔ basos, posterior margin has about 4 pairs of long setae. Carpus width ½ length, length ⅓ basos; seta or 2 anterodistally, posterior margin has 2 long single spines, a few setae. Propod nearly ½ basos length, width less than ⅓ length; posterior margin has 3 or 4 small spines. Strong dactylos ½ propod length, a single seta posteriorly. Fourth. Basos ovate, width ⅔ length, margins slightly convex, anterior has about 7 groups of 1 or 2 spines or setae; posterior has about 8 single fine setae. Ischium less than ⅓ basos length, spine and seta on anterodistal angle. Merus narrowing a little
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Text-fig. 3.—Phreatogammarus propinquus Chilton. Female. 39—Antenna 1. 40—Gnathopod 1. 41—Gnathopod 2. Phreatogammarus helmsii Chilton. 42—Left mandible, spine-row and cutting edge. 43—Mandibular palp. 44—Gnathopod 1, male 45—Gnathopod 2, male 46—Gnathopod 2, sideplate ventral margin 47—Peraeopod 1, male, propod and dactylos 48—Peraeopod 1. female 49—Peraeopod 1, female, dactylos. 50—Peraeopod 2 sideplate. 51—Peraeopod 3 basos. 52—Peraeopod 5 basos.
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proximally, width ⅖ length, length ¾ basos, both margins have 2 single spines, anterodistal angle has 2 spines, posterodistal has 1, a few setae beside spines. Carpus width less than ⅓ length, barely shorter than merus, margins with groups of 2 or 3 spines medially; distal angles with spine and a few setae. Propod ⅘ basos length; width about 1/7 length; linear; both margins with 2 groups of 2 or 3 long spines, distal margin has several very long spines. Stout slightly-curved dactylos ⅖ propod length.
Urosome First segment with a strong single spine ventrally just anterior to 1st uropod insertion.
Uropods. Second reaching no farther than 1st; 1st, peduncle longer than rami, 4 spines on outer dorsal margin, very strong spine at outer distal angle; 2nd, rami and peduncle subequal; rami of botli appear to have 1 spine or possibly 2 in middle of ramus; several strong end spines; peduncle has 1 or 2 spines on outer dorsal margin. Telson: Long fine spines on end.
Locality Mount Anglem, Stewart Island, New Zealand.