SCIENCE-GOSSIP. 



91 



of the shell was turned too far to the left. Fig. 8a 

 shows the same shell with part of the outer wall 

 removed, from which it will be seen that the 

 arrangement of the plates is similar to that in 

 Gorilla fryae and C. erronea ; there is, however, 

 what appears to be a small adventitious palatal 

 plate or tooth between Nos. 3 and 4, but this 

 was not found to be constant in other specimens 

 of this species which I examined, and it may 

 therefore be assumed that this is an abnormal case. 

 Since writing the above, Mr. Ponsonby has kindly 



placed at my disposal two 

 immature specimens of 

 C. rivolii, the examination 

 of which bears out the 

 statement already made, 

 that plates are formed at 

 the various stages of 

 growth, which are after- 

 wards absorbed. These 

 two specimens are shown 

 in figs, ga-gf, of which 

 a-e exhibit one with four 

 whorls completed, having five palatal plates, which 

 resemble those of Gorilla fryae (figs. 5 and 6) in 

 being different in character from the mature plates. 

 Here again they are much broader, they are also 

 seen to be triangular, to overlap and to reach 

 almost to the inner wall ; no parietal plates are 

 present. In fig. ga the palatal plates are shown 

 as seen on looking into the aperture, in fig. gb 

 they are looked at more from below, the shell 

 being tilted a little. In figs, gc and gd they are 

 shown as seen externally through the shell- 

 wall. In fig. ge the same specimen is depicted, 

 seen from above, the dagger indicating the place 



Fie. 8. — Corilla rivolii. 



h %. 



d 

 Fig. 9. — Corilla rivolii immature. 



where the plates are found. Fig. g/ shows another 

 immature specimen, the dagger here also indicating 

 the position of the plates ; but while in the former 

 specimen they are placed at the end of the fourth 

 whorl, they are here found at a place where only 

 three and-a-half whorls have been completed. 

 Lt.-Col. H. H. Godwin Austen, in a letter, 

 confirms my surmise as to the temporary character 

 of these plates, stating that those found in the old 

 shells differ very much from what those found in 



the young might be supposed to develop into. He 

 thinks that the early folds are absorbed to make 

 way for subsequent ones. As will be seen from the 

 consideration of Gorilla odontophora further on, 

 however, this is not always the case, since in one 

 mature specimen I have found the immature 

 palatal folds still existing. 



Gorilla odontophora does not seem to be well 

 understood, and the figure given in Tryon's 

 "Manual of Conchology " (2), iii., t. 33, f. 34, 

 copied from Hanley and Theobald's " Conchologia 

 Indica," t. 57, f. 6, is somewhat misleading, as it 

 evidently represents an immature specimen, show- 

 ing the palatal folds as they appear from the 

 aperture, but no reference is made to this fact. 

 Mr. Ponsonby having in his possession two mature 

 specimens, which he doubtfully referred to this 

 species, kindly permitted me to open one, which is 

 shown in figs. loa — lot^. On reference to fig. lob it 



Fig. 10. — Corilla odontophora. 



will be seen that only two parietal folds are 

 present, corresponding to Nos. 2 and 3 in the 

 previous species. Fig. loc exhibits the plates as seen 

 from behind their inner terminations, and it will be 

 observed that there are four palatal folds, the 

 upper three of which are shown through the wall 

 of the shell in figs, lod and lo^, while fig. loa shows 

 the entire shell from below (restored), with plates 

 Nos. 3 and 4 showing through. On comparison 

 with the figures of Gorilla erronea and Gorilla fryae, 

 it is seen that in Gorilla odontophora the palatal 

 folds are much shorter and less flexuous than in 

 the two former, and, as correctly stated by Benson 

 in describing this species ("Annals and Magazine of 

 Natural History " (7). xvi, 1865, p. 175), they "are 

 entirely visible from the aperture." Another point 

 to be noted is that the outer terminations (i.e. nearest 

 the aperture) of the upper three palatal folds form 

 an oblique line parallel with the peristome, Ibe first 

 one being nearest the aperture, while in GcHHa 



