OCR Text |
Show 1891.] LAND-SHELLS FROM BORNEO. 41 Unfortunately the figure is taken from the worse of the two specimens, which is hardly mature. The shell in spirit was fully grown, but was broken in extracting the animal. It is, however, an easily recognizable species; the spirit-specimen had a strongly marked white callus on the surface of the penultimate whorl within the aperture. Description of first specimen dissected.-Animal dark coloured, with the pallial margin pale, an overhanging very long hooked lobe above the mucous pore. Right dorsal lobe moderately large, the left anterior dorsal lobe small, black ; the posterior pale and extending backwards, thus it is in two lappets (see Plate IV. fig. 5 a). A small tongue-like right shell-lobe evidently capable of great expansion flatly over the shell, as it is very solid and contracted in the spirit-specimen ; a well-developed flat triangular left shell-lobe. The foot is divided. This specimen got accidentally brushed off the slide,and the drawing given was made from another not so well preserved ; the right shell-lobe is torn and the left destroyed, but it shows the form of the dorsal lobes. The odontophore (fig. 5 b) consists of a central, simple, unicuspid tooth, succeeded by an innumerable number of similar bicuspid teeth, the cusps being of nearly equal length and terminally placed. The jaw is broad and straight on the cutting-edge. The odontophore may be compared with that of Durgella minutu, described by me from the Khasi Hills (Land and Freshwater Moll. of India, p. 144, pi. xxxix.). But better preserved and fresher specimens are required of these small mollusks, and the anatomy should be also examined soon after death, to enable us to accurately understand how they are related to each other. TROCHOMORPHA PLANORBIS. LLelix (Carocol/a) planorbis, Less, in Duperrey, Voy. Coquille, Zool. ii. p. 312 ; Atlas Moll. pi. xhi. fig. 4 (1830). Helix planorbis, Pfeiff. Monogr. Helic. i. p. 122 (1848), et v. p. 187 (1868) ; Mousson, Moll, von Java, p. 25, pi. ii. fig. 9 (1849) ; Ludeking & Smit, Nat. Tijdschr. Nederl. Indie, xxi. p. 97 (i860). Helix approximata, Le Guillou, Rev. Zool. 1842, p. 139 ; Pfeiff. Monogr. Helic. i. p. 206 (1848); Reeve, Conch. Icon. pi. cviii. fig. 603(1852). Trochomorpha appropinquata, approximata, etjavanica, v. Martens, Monatsber. Akad. Berlin, 1864, p. 267 ; Pfeiff. Monogr. Helic. v. p. 187 (1868). Trochomorpha plunorbis, Wall. P. Z. S. 1865, p. 408 ; v. Martens, Preuss. Exped. Ost-Asien, Landschneck. p. 249, t. xiii. figs. 4, 7, 8 (1867). Var. A P P R O P I N Q U A T A , v. Martens, Preuss. Exp. Ost-Asien, Landschneck. p. 249, t. xiii. fig. 8 (1867). Hab. Niah Hills. Issel gives two other varieties of planorbis from Sarawak-lessoni, v. Martens, and nummus. |