SCIENCE-GOSSIP. 



In the fiuviatile bivalves, spines are practicallv 

 unknown, with the striking exception of Utiio 

 spinosus, of Georgia, U.S., and the Nile Oyster, 

 JEtheria c a ill audi. 



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 or costulation (0. bari tense) 

 to the form (0. grandispinosum) in which the spines 

 assume such a marvellous perfection. In 0. wallacei, 

 named by M. Ancey in honour of Dr. A. R. Wallace, 

 the whorls are angulated at the middle, as if in- 

 dicating the place from whence the spines would 



Opisthostoma mirabile (Enlarged). 

 I 



eventually develop. In 0. jucundum they make 

 their first appearance, in 0. pulchellum they are 

 still more pronounced, 0. everetti exhibits yet 

 further development, the maximum being reached 

 in 0. mirabile and O. grandispinosum. The former 

 of these, originally described by the author of 

 these notes, 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 (for it is but two lines in length, and in 

 its entirety weighs only one twenty-fifth of a grain) 

 increases our admiration of its perfection. No 

 creation of the mind could approach the elegance 

 and finish of its design. The fragile tapering 

 spire of a pale-brownish tint, the erect glassy 

 hollow spines bristling all round the middle of 



Opisthostoma grandispinosum {Enlarged). 



the volutions, the more curved ones curling 

 beneath the base, the trumpet-like aperture de- 



fended behind, as it were, by a shield of glass — 

 these are some of the principal characteristics 

 of this most delicate and wonderful structure. 

 0. grandispinosum is perhaps scarcely as graceful, 

 if we may venture to criticise Nature's handiwork, 

 but far more grotesque in appearance. It 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 produced 

 and contorted makes it quite difficult to follow the 

 design of the shell itself. Up to a certain period, 

 that is, up to the commencement of the body- whorl, 

 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 quite difficult, without con- 

 sideration, to say whether it is a dextral or 

 sinistral shell we have before us. Probably 

 the majority of people would, however, at first 

 sight, guess wrongly upon this point with regard 

 to all the other Bornean forms, for the aperture 

 are so decidedly on the left of the spire. This, 

 however, does not in reality make them sinistral 

 shells, but the left-handed appearance arises 

 merely from a peculiar twist and retroversion of 

 the body-whorl which turns the aperture back- 

 wards. If, therefore, we place the opening towards 

 the eye, as seen in the figure of 0. mirabile, 'the 

 spire being upward, it appears on the left side of 

 the shell as in normally sinistral forms. 



One question remains to be asked. To what end 

 is all this extraordinary development of sculpture ? 

 We can well suppose in the case of the succulent 

 murex and cockle, to be covered all over with 

 strong bristling spines would make the hungry fish 

 shy of attack ; but in the case of these tiny 

 Opisthostoma, one would almost imagine that their 

 bodies, a mere microscopic film, would hardly be 

 worth attacking. Yet some carnivorous beetle 

 may rove about in Borneo in the home of these 

 little creatures, whose onslaught maybe averted by 

 the bristling array of spikes. Some happy bird, 

 always pecking at something, may hesitate to prick 

 its tongue, some other creature — but enough, we 

 are entering the realm of speculation. That this 

 marvellous "sculpture " has its meaning and is of 

 some advantage to its possessor, we may rest 

 assured, but that we shall ever fathom its purpose, 

 is less than likely. 



British Museum, South Kensington ; 

 Feb., 1894. 



