126 



SCIENCE-GOSSIP, 



ARMATURE OF HELICOID LANDSHELLS. 

 By G. K. Gude, F.Z.S. 



(Contiimed from page 92.) 



TN my last article, in speaking of Gorilla humberti, 

 I stated that only two specimens were known 

 to me to exist in collections, and that these were 

 in the possession of Dr. Brot, who described the 

 shell. Since writing, however, Mr. Ponsonby has 

 shown me a specimen, which, upon being opened, 

 proved to pertain to that species, although it is 

 considerably less rounded in outline. The palatal 

 tooth corresponds in size and position to that 

 in Dr. Brot's shells, but the parietal fold extends 

 much further back, a fact which confirms my 

 surmise that this fold in the shell figured by 

 Dr. Brot (and by me, fig. 11, ante p. 92) had 

 been damaged in the 

 cutting process. Colonel 

 Beddome has informed 

 me that he possesses 

 three specimens of this 

 species, which he has 

 obligingly sent to me 

 for inspection ; one of 

 these agrees with Mr. 

 Ponsonby's shell in 

 being somewhat oblong, 

 while the other two 

 conform to Dr. Brot's 

 types as regards outline. 

 The species certainly 

 appears to be less rare 



than was at first supposed, and it may turn up in 

 other collections. 



We have now dealt with Gorilla cliarpentieri, C. 

 fryae, C. erronea, C. rivolii, C. odontophora, and C. 

 humberti. The only other species of the genus at 

 present known, are C. anax, Benson, and C. bed- 

 domeae, Hanley. 



The two species last named, with which we are 

 here concerned, form a separate group in the genus, 

 and, from considerations which will be explained 

 further on, may be looked upon as being the oldest 

 members of the group provided with plates. Gorilla 

 cliarpentieri being the primordial form. This group 

 of Gorilla anax (including C. beddomeae), is of equal 

 value to the group of Gorilla erronea (including G. 

 fryae, G. rivolii, G. odontophora and C. humberti) and 

 to the remaining group of Gorilla charpentieri. 



Gorilla anax is shown in figs, iza-e, the 

 drawings having been made from a specimen in 

 Mr. Ponsonby's collection. It is the only species 

 of Gorilla known to occur outside Ceylon, being 

 found, as already stated, in the southern part of 

 India. It is of a dark chocolate colour, and 

 possesses three parietal and four palatal plates. 



Fig. 12. — Gorilla anax. 



Fig. 12a shows the entire shell, four of the plates, 

 two parietal and two palatal, being visible from 

 the aperture. The parietal plates are much 

 broader than in the other species. No. i curves 

 upwards, while No. 2 reaches as far as the 

 parietal callus ; but, unlike those of the other 

 species, they are separate.- No. 3 parietal plate is 

 almost horizontal, with but a slight curve, as will 

 be seen on reference to fig. 12c, the specimen 

 being there figured with the outer wall removed. 

 Fig. i2d shows the same shell with part of the 

 outer wall broken away, and the plates are shown 

 as they appear from behind their inner termina- 

 tions. The palatal 

 plates also are seen to 

 be much broader than 

 in the other species, and 

 the three upper ones 

 are much more oblique, 

 resembling in this re- 

 spect the immature 

 plates found by me in 

 three of the other 

 species. In fig. lie a 

 portion of the last whorl 

 is drawn, in which the 

 palatal plates Nos. i, 2 

 and 3 are shown as 

 they appear through 

 the shell, while fig. 12& shows the entire shell from 

 below with palatal plates Nos. 3 and 4 shining 

 through. Colonel Beddome has been so good as to 

 lend me several adult examples of this species for 

 examination, one of which is of interest from the 

 fact that it exhibits, in addition to the mature arma- 

 ture, immature plates which are identical in form 

 and position with those I found in an adult shell 

 of Gorilla odontophora, and described in my previous 

 article (ante p. 92). With these adult examples 

 was an immature shell with three whorls com- 

 pleted, which is specially noteworthy in that it 

 possesses two sets of immature plates, one near the 

 end of the third whorl, and the other a little beyond 

 the place where two and a-half whorls have been 

 completed. It may therefore safely be inferred that 

 the plates are not absorbed till after completion of 

 the new ones, and it will be remembered that this is 

 not an isolated case, for, as already stated, two sets of 

 plates were observed by me in a full-grown speci- 

 men of Gorilla odontophora, and Colonel Beddome 

 lent me a shell of this last-named species, identical 

 in this respect. Colonel Beddome informs me 

 that he collected his specimens of Gorilla anax on 



October, 1896. — No. 29, Vol. 3. 



