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Volume 37, 1904
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Corneocyclas novozeelandica, Prime (1862).

P.Z.S., 1862, p. 3.

(1.) Lake Waikare (Stat. 29—From weeds in 1½ ft. to 2 ft.).—Nine specimens of different size; colour greyish-yellow, shining, inequilateral, with fine concentric lines, which are crossed by close microscopic radiate striæ. Nepionic shell convex, concentrically striated, well delimited, but passing without any change into the disc of the adult valve. Ligament inset. Right valve with the two cardinals remaining united, crescent-shaped; four laterals. Left valve with two cardinals, the posterior bifid, the anterior triangular; two laterals. The accompanying fig. 8 shows the characters of the hinge.

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Fig. 8

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Four specimens were measured—Length, 2¾–5 mm.; height, 2½–4 mm.; diam., 1¼–2½ mm.: and the mean indices are—iii. = 83; vii. = 48; x. = 59.

These specimens are very much like those I collected in the River Avon, Christchurch.

(2.) Lake Waikare (Stat. 29F—From weeds in 1½ ft. to 2 ft.).—Four specimens, dead when collected. They do not differ much from those of Stat. 29, except being slightly more globular. The dimensions of three specimens measured are—Length, 5 mm.; height, 4½ mm.; diam., 3¼ mm.; umbo 3 mm. from anterior margin: length, 4¼ mm.; height, 3½ mm.; diam., 2¼ mm. umbo 2½ mm. from anterior margin: length, 3 mm.; height, 2½ mm.; diam., 1½ mm.; umbo 1¾ mm. from anterior margin. The mean indices are—iii. = 85; vii. = 56; x. = 58.

(3.) Lake Wakatipu (Stat. 17—Dredged with weeds in 20 ft. to 100 ft.).—One minute specimen, rounded, yellowish-white, subequilateral. Length, 2¼ mm.; height, 2 mm.

This small specimen has the aspect of a Sphærium, but the nepionic shell is so distinct that I prefer placing it in Corneocyclas for the present. I tried to separate the valves, but could not do it without running the risk of breaking the valves. Without ample material, and especially examining the living animal, it is impossible to be quite certain about its generic position.

(4.) Lake Wakatipu (Stat. 34—Dredged in 10 ft. to 30 ft.).—One adult and four young specimens. The adult is light-brown, the nepionic shell distinctly limited; the young examples are grey to yellowish, more inequilateral and tapering in front. The dimensions of two specimens are—Length, 5¼ mm.; height, 4½ mm.; diam., 2½ mm.; umbo 2¾ mm. from anterior end: length, 3½ mm.; height, 1¾ mm.; diam., 1½ mm.; umbo 2 mm. from anterior end: and the mean indices are—iii. = 83; vii. = 46; x. = 55.

There is one specimen, covered with a black coating, which is suborbicular, much compressed, inequilateral, with inconspicuous beaks, the anterior side broadly rounded. The dimensions are—Length, 4 mm.; height, 3¼ mm.; diam., 1½ mm.; umbo 2½ mm. from anterior end: and the indices are—iii. = 81; vii. = 38; x. = 62. I have seen similar abnormities amongst specimens I collected in the River Avon.

(5.) Lake Manapouri (Stat. 13—Dredged in shallow water near the shore).—Three young specimens, which are at once recognised as being Corneocyclas, being more inequilateral, compressed and attenuated anteriorly than adult specimens. Had I not seen the same forms from other localities, collected together with adult examples, I might have been inclined to consider

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them a distinct species. With few exceptions the young shells of C. novozeelandica show the characters just indicated. The colour is light-grey, and the nepionic shell is distinct. The dimensions of two specimens are—Length, 3¼ mm.; height, 2¾ mm.; diam., 1½ mm.; umbo 2 mm. from anterior end: length, 2¾ mm.; height, 2 mm.; diam., 1 mm.; umbo, 2 mm. from anterior end. The mean indices are—iii. = 78; vii. = 41; x. = 66.