yiyi^c.»i<. j^- /^ ■ ^ 



88 



SCIENCE-GOSSIP. ^^^^ 



ARMATURE OF HELICOID LANDSHELLS ; 



And a New Species of Gorilla. 

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



' I "HAT Mollusca have numerous enemies is a 

 fact well known to naturalists, for not only 

 do they serve as food for many mammals, birds 

 and reptiles, but they are preyed upon by some 

 insects, and even by other mollusca. Naked slugs 

 are especially exposed to the attacks of birds, slow- 

 worms and snail-slugs (Testacella) ; and, in foreign 

 countries, of carnivorous snails, such as Glandina 

 and others. Shell-bearing Mollusca likewise are 

 devoured by birds and mammals ; they have 

 besides many insect enemies, particularly under 

 tropical climates, and we shall, therefore, not be 

 surprised to find that in several instances tliese 

 creatures have come to be provided with special 

 means of protection. This has been attained in 

 various ways, indirectly by protective resemblance 

 between the forms or colours of the shells and 

 their immediate surroundings ; or, directly, by 

 special structures, such as teeth, plates, or constric- 

 tions, serving as buttresses or barricades behind 

 which the animal can withdraw. It is probable, 

 however, that these structures may at the same 

 time help to strengthen and support the outer wall 

 of the shell, and in this manner safeguard the 

 mollusc against injuries, accidental or otherwise. 



In the following notes I propose to consider the 

 several special structures or forms of armature, 

 just indicated, as they are found in many of the 

 genera of Helicidae, which have come under my 

 .notice. It will, of course, be understood that the 

 operculum, which is so generally present in marine 

 mollusca, and in the land and freshwater shells 

 taxonomically associated with them, and the 

 clausilium or elastic door, which characterizes and 

 gives its name to the well-known genus of land- 



shells Clavsilia, are also means of protection ; but 

 they do not form an integral part of the shell, and 

 I do not propose to consider them here. A point 

 to be noticed with regard to the armatures under 

 consideration is that they are not the exclusive 

 property of any particular genus, or wider group, 

 but occur in various genera or groups, often of 

 distant affinity. 



I. Gorilla. 



The Helicoid genus Corilla, with which we are 

 concerned in the first place, is an interesting group 

 of landshells inhabiting the jungles of Ceylon, 

 with a single outlying species in the southern 

 point of the Indian Peninsula. The armature, 

 which sometimes exhibits considerable complica- 

 tion, consists generally of a variable number of 

 revolving plates or folds on the inner side of the 

 shell - wall. It may be 

 mentioned as a curious 

 fact that a single species, 

 namely Corilla chai'pcn- 

 tieri (Geylon), is devoid 

 of armature (fig. i). 



I was favoured not 

 long ago by Mrs. R. S. 

 Fry, of Singapore, with 

 some shells collected by 



her during a stay of several months in Ceylon ; 

 amongst these were eight specimens of a shell which, 

 at first, I was inclined to refer to Corilla odontophora, 

 of Benson, but, after some research and careful 

 comparison with allied forms, it became evident 

 that I had to deal with a new form. It is probable, 

 however, that it already exists in collections, as 

 Mr. Hugh Fulton sent me a specimen labelled 



Fig, I.— Corilla clunpentioi. 



