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Show 1891.] LAND-SHELLS FROM BORNEO. 29 closing towards the posterior end and contracted for a short distance into a tube, the retractor muscle being at the junction of the yas deferens. The spermatheca is very and unusually long, extending to the albumen-gland; it rises from another pear-shaped muscular sac, on the side of which the oviduct enters. There is nothing remarkable about the ovo-testes or albumen-gland. The odontophore (Plate VI. fig. 8).-The form of the median teeth very gradually merges into that of the laterals, which become at last little short straight teeth. The central teeth are all unicuspid, the central tooth of all being triangular in form ; the formula is 109 . 43 . I . 43 . 109 152 . 1 . 152. The lingual ribbon I extracted is nearly perfect, not a row was lost, and it contains 177 rows, giving the enormous number of 54,000 teeth. The jaw (Plate VI. fig. 7) has a low central projection, and is not much bent. The character of this animal differs so widely from those in genera with which it is now associated that it does not seem at all in the position it should occupy, and with R. ovum and others will have to be moved. As I have only been able to obtain one example of R. brookei in spirit, it is better to wait until others are examined before doing so. Nanina (Ryssota) borneensis. Helix borneensis, Pfeiff. P. Z. S. 1849, p. 127; id. Monogr. Helic. iii. p. 70 (1853), et. v. p. 114 (1868) ; Reeve, Conch. Icon. pi. cxcvi. fig. 1379 (1854). Nanina borneensis, v. Martens, Preuss. Exped. Ost-Asien, Landschneck. p. 238. DYAKIA, gen. nov. (Type, Helix hugonis, Pfeiff.) No shell-lobes to the mantle, and the dorsal lobe much reduced in size. Shells generally sinistral. Hitherto placed in Ariophanta. The amatorial organ of peculiar form, with a calcareous dart or sagitta amatoria. For further description of details see D. hugonis. DYAKIA HUGONIS. (Plate V. figs. 5-5 b.) Helix hugonis, Pfeiff. P. Z. S. 1863, p. 523; id. Novitat. Conch. iii. pi. lxxiv. figs. 1, 3 ; id. Monogr. Helic. v. p. 81 (1868). Helix sinistra, Bonnet, Rev. Zool. 1864, p. 67, pi. v. fig. 2. Nanina (Hemiplecta) hugonis, v. Martens, Preuss. Exped. Ost- Asien, Landschneck. p. 225 (1868). The anatomv of Hemiplecta humphreysiana, Lea, from Singapore, the type of the genus, which I have examined and alluded to before, differs widely from that of H. hugonis. Hab. Two specimens from Trusan, and one dextral variety from the Niah Hills (A. Everett). |