1891.] LAND-SHELLS FROM BORNEO. 41 



Unfortunately the figure is taken from the worse of the two speci- 

 mens, 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 ofl'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 minuta, 

 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. 



Helix (Carocolla) planorbis. Less, in Duperrey, Voy. Coquille, 

 . Zool. ii. p. 312 ; Atlas Moll. pi. xiii. 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 (1860). 



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. BerUn, 1864, p. 267 ; Pfeiif. Monogr. Helic. v. 

 p. 187 (1868). 



Trochomorpha planorbis, yV all. P. Z. S. 1865, p. 408 ; v. Martens, 

 Preuss. Exped. Ost-Asien, Landschneck. p. 249, t. xiii. figs, 4, 7, 8 

 (1867). 



Var. APPROPiNdUATA, V. Martens, Preuss. Exp. Ost-Asien, Land- 

 schneck. p. 249, t. xiii. fig. 8 (1867). 



Hub. Niah Hills. 



Issel gives two other varieties of planorbis from Sarawak — lessoni, 

 V. Martens, and nummus. 



