63 



investing the surface. Land shells, as a rule, are not 

 remarkable for any very prominent ornamentation of the 

 surface, such as obtain among the marine Gasteropods ; 

 their beauty lies rather in the marvellous variety of their 

 form of coloration. We find the exterior in the majority 

 of cases more or less even. True, among the Clausillas, the 

 Strophias, and Helicidse many species exhibit longitudinal 

 riblets, but few species of land molluscs exhibit thorny pro- 

 cesses of any importance. Fresh-water shells, like the terres- 

 trial forms, are, as a rule, also devoid of spines, but here 

 again there are some exceptions. In two or three species 

 only of the Bornean Opisthostoma prickly adornment attains 

 remarkable development. 



" There is a perfect gradation from shells with rounded 

 whorls ornamented with simple oblique striation, like 

 O. baritense, to the form O. grandispinostivi, in which the 

 spines assume such a marvellous perfection. In 0. wallacei 

 the whorls are angulated at the middle, as if indicating the 

 place from whence the spines would eventually develop. In 

 0. jncnndum they make their first appearance, in O . pnlchclhnn 

 they are still more pronounced. O. evcrctti exhibits yet 

 further development, the maximum being reached in O. mira- 

 hilis and O. grandispinosmn. The former of these is more 

 beautifully graceful and more delicate in structure than the 

 latter, — indeed, it is difficult to recall among all the thousands 

 of marvellous forms of land shells any as strikingly wonderful 

 as this tiny creation of beauty ; its minuteness increases our 

 admiration of its perfection. The fragile tapering spire of a 

 pale brownish tint, the erect glassy hollow spines, bristling 

 all round the middle of the volutions, the more curved ones 

 curling beneath the base, the trumpet-like aperture defended 

 behind as it were by a shield of glass, — these are some of the 

 principal characteristics of this most delicate and wonderful 

 structure. 



"Grandispinosuin has a very spider-like look, the spines 

 curling over like so many claws ready to clutch an enemy. 

 The curious manner in which the last whorl is contorted 

 makes it difficult to follow the design of the shell itself. Up 

 to a certain period it has the normal appearance of a dextral 

 conical shell ; the last volution then commences its erratic 

 course, making a complete curve up the spire and then to 

 the right, carrying the aperture even above the apex. This 

 peculiar production of the whorl makes it difficult without 

 consideration to say whether it is a dextral or sinistral shell 

 we have before us. 



