The specimens described in this Synopsis (Ann. & Mag. Nat. Hist. 1S40) were either in the collection of 

 the British Museum or in that of the Zoological Society, which includes the specimens discovered by Mr. 

 Cuming during his residence in South America, and presented Ijy him to the Society. 



Those described in the paper in the 'Proceedings of the Zoological Society' for 1847, which is reprinted 

 in the ' Annals and Magazine of Natural History ' for the same year, are all contained in the collection of the 

 British Museum. Unfortunately, when the Zoological Society distributed its Museum, several of the species 

 of Starfish which had been brought home by Mr. Cuming and described in my first paper could not be found ; 

 and as the time when and how the specimens disapi)carcd could not be discovered, there was no means of 

 traciu"- the type specimens and procuring them, like other type specimens of that collection, for the British 

 Museum. 



The hard parts of these animals, whether they are in the form of tessera', as in the Echidna, or of ossicula, 

 as in the IL/postomala, or in that of spines, as in either, are evidently the hardening of certain parts of the 

 cellular substance or skin, and these hard parts retain their organization and vitaUty during the life of the 

 animal; consequently they are not inorganic secretions, like the shells of mollusca, as they have generally 

 been considered, but have far more relation to bones and coral, and like them form a peculiar kind of body, 

 intermediate between shells and the skeletons of vertebrata. " These pieces," as I have observed in the 

 ' Synopsis of the British Museum,' " are formed by the earthy particles being deposited round certain definite 

 sjrots in the skin ; and as they are developed they assume a definite arrangement into certain distinct shapes 

 peculiar to the difterent kinds. Although these are strongly united together by the skin, and have a kind of 

 organization during the life of the animal, they may easily be separated from each other after death, and then 

 appear like separate bones. This structure allows the animal to increase both the size and the number of the 

 ])ieces that compose its protecting case as the body grows, and also to repair, by the deposition of fresh calca- 

 reous particles on the skin of the healed part, any injury which the animal may have received from external 

 accidents during its life." 



This structure is not so easily demonstrated in the internal ossicula of the Starfishes as it is in the external 

 tesserae of the Sea-eggs and in the spines of both these kinds of animals, as they are often to be found broken 

 and repaired during their growth ; and this repair does not take place by any secretion applied to their sm-face, 

 but by a healing of the part, which leaves a scar on the surface. Nevertheless the entire similarity which 

 exists between the external spines and the internal tubercles at once shows that they are of the same structure ; 

 and this is further proved by the examination of the tubercles of those kinds which are in great part exposed 

 on the surface, as is the case with the different kinds of Pentaceros, where the development of these hard 

 parts can often be observed during the process of reproducing an arm that has been accidently injured or 

 destroyed. 



