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SCIENCE-GOSSIP. 



mouth, following for some distance the curvature 

 of the second parietal plate, it is almost in 

 juxtaposition with the latter ; the third palatal 

 plate also curving upwards, terminates below the 

 third parietal one which curves downwards, and 

 they therefore cross each other about the middle ; 

 No. 4 is situated very low down, close to the 

 junction of the outer with the inner wall, and 

 proceeds in an almost horizontal direction. These 

 palatal plates are distinctly visible externally 

 through the shell, and they are thus shown in 

 figs. 4c and ^d, the latter figure exhibiting Nos. 

 I, 2 and 3, while the former shows Nos. 2, 3 and 4. 

 The specimens delineated in figs. 2 and 4 are all 

 mature, and as in this condition they are composed 

 of 5 whorls, it follows that the plates are placed 

 near the end of the fifth whorl. In fig. 4/ the 

 palatal plate No. 2 is shown by itself, the upper 

 convex line indicating its attachment to the shell- 

 wall. An interesting fact was revealed by the 

 examination of an immature specimen received 

 with the others ; on breaking away the walls at 

 various points, five palatal plates were observed in 

 the fourth whorl, at a point which would be inter- 

 sected by a line from the apex of the shell to the 



and laminae of the Pupidae, observed that "they 

 may answer the purpose of an operculum to keep 

 out enemies, while they afford no obstacle to the 

 motions of the soft and yielding body of the 

 animal" ("Zoological Journal," iv., 1829, p. 168, 

 footnote). As illustrating the vulnerability of 

 unarmed shells, it may be mentioned that Jeffreys 

 found a half-grown specimen of Helix strigella 

 containing the larvae-form pupa of Drilus flavescens, 

 the female of which has been named Cochleoctonus 

 vorax from its snail-eating habit. He also found 

 a similar pupa in a Helix incarnata, which, as in the 

 case of Helix strigella, completely occupied the spire 

 of the shell, of which it had devoured the former 

 inhabitant ("Annals and Magazine of Natural 

 History" (3), vi, i860, p. 348). Of much interest 

 is a note by Lt.-Col. Godwin Austen, who, in a 

 paper on the Asiatic landshell genus Plectopylis, 

 states that "when breaking up a number of shells 

 to expose the barriers and ascertain if their char- 

 acters were constant, I was greatly interested to 

 find in two instances the presence of small insects 

 that had become fixed between the teeth." He 

 further remarks that those shells possessing such 

 bars to the predatory visits of insects, such as 



Figs. 5 and 6. — Gorilla fryae, immature x 2. 



Fig. 7. — Gorilla erronea. 



point where the plates would be found in the mature 

 shells. This specim^en is represented in figs. 5 

 and 6. On reference to fig. 5 it will be seen 

 that the upper four of these plates are much 

 broader than those of the mature shells, as they 

 reach nearly to the inner wall and overlap, 

 being placed close together, slanting upwards, but 

 scarcely curving ; No. 5 is very short and narrow, 

 and corresponds in position to No. 4 in the older 

 shells ; fig. 6 shows the upper four plates in their 

 immature position as seen through the shell. No 

 plates being found in the fourth whorl of the 

 mature shells, the inference is that as the shell is 

 completed the plates first formed are absorbed by 

 the animal, and this fact supports the view that 

 the plates form barriers to exclude predatory 

 insects. It may also be assumed that the animal 

 produces similar plates from an early stage of its 

 existence, absorbing them as each successive 

 whorl with its complement of plates is completed ; 

 but this of course can only be demonstrated by the 

 examination of a series of shells in various stages 

 of growth. That structures of this kind serve as a 

 means of defence was suggested as long ago as 

 1829 by Guilding, who, in speaking of the teeth 



certain kinds of beetles, ants, or even leeches, all 

 of which swarm in the forests where the shells 

 are found, would have the best chance of sur- 

 viving. (" Proceedings of the Zoological Society 

 of London," 1874, p. 611.) 



In fig. 76, a portion of the inner side of the 

 outer wall of the allied species. Gorilla erronea 

 (Ceylon), is shown with the plates iyi situ, disposed 

 in much the same manner as in Gorilla fryae ; they 

 are, however, shorter and less curved ; the parietal 

 plates are almost identical in position and shape 

 with those of Gorilla fryae, as shown in fig. ja, but 

 they are shorter and the union of Nos. i and 2 is 

 not so complete. Fig. 7c shows a specimen side- 

 ways, which is of interest on account of a small 

 adventitious tooth between palatal plates Nos. 2 

 and 3. 



In figs. 8a and Sb Gorilla rivolii, of Deshayes 

 (Ceylon), is delineated, the latter figure showing 

 the remarkably reflected lip, and the three parietal 

 plates, of which Nos. i and 3 are much more 

 exserted than in the two' previously-mentioned 

 species ; the palatal plates also reach much nearer 

 to the edge of the lip than in the other two species, 

 but they are not shown in the figure, as the mouth 



