REPORT ON THE ASTEROIDEA. xxiii 



believe, would not meet with general acceptance on other grounds, as the Asteroidea are by- 

 many considered to represent a more archaic type than the Echinoidea. 



(3.) As to whether the pedicellariae furnish characters by which the four "orders" 

 indicated by Perrier may be distinguished, I consider that they are insufficient and 

 unsatisfactory ; and I would venture to say that in my opinion two of the orders in 

 question would be more correctly described as defined by the character of their spinulation. 

 I refer to the Spinuloses and the Paxillosae. In his diagnosis of the order Spinuloses 

 (Echinulatae), Perrier distinctly states that the pedicellariae are simply formed of modified 

 spinelets (op. cit., p. 206), and in that of the order Paxillosae (op. cit., p. 249) no mention 

 whatever is made of pedicellariae ; in the abridged synopsis of the orders, however, given 

 above, the Paxillosae are defined as characterised by pedicellariae, formed of an ossicle of the 

 skeleton and the spinelets which cover it (op. cit., p. 154). The statements in the case of 

 these two " orders " would seem to negative Perrier 's argument that pedicellariae are not 

 modified spinelets and that they have nothing to do with those appendages. Furthermore, 

 I fail to see that the characters invoked from the modifications in the form of the pedi- 

 cellariae are of sufficient importance to indicate differences of an ordinal degree. 



Apart from the above considerations, which negative the view that the pedicellariae in 

 the Asteroidea afford characters by which orders may be distinguished, I make bold to 

 say that I am unable to regard either pedicellariae, or spines, or any other mere tegu- 

 mentary appendages as furnishing characters of sufficient importance to warrant their 

 employment as taxonomic factors of ordinal rank. Though I admit that pedicellariae do 

 possess characters of a certain taxonomic value, I cannot regard them as characters either 

 of primary or even of secondary importance in the great question of the division of a class. 



I may remark in passing that I do not consider the plate to which Viguier has unfor- 

 tunately given the inappropriate name of " odontophore" to merit the importance which 

 he has placed upon it. The plate in question, which is the basal plate of the interbrachial 

 system, is pushed by development upon the first pair of adambulacral plates, or mouth- 

 plates, and is moulded into form to a certain extent by these plates, its shape being largely 

 dependent on the number of the rays and the character of the adambulacral plates. So 

 far, however, as my own observations go, I am inclined to think that in not a few cases 

 greater differences may be found to exist between the "odontophores," or, as I should 

 prefer to call them, "basal interbrachials," of congeneric species, than between those of 

 species of distinctly separate genera. The form of the plate appears to be extremely 

 variable, and not to present characters of very great taxonomic value. 



III. A Classification of the Asteroidea based on Factors of Morphological Importance. 



Passing in review the various morphological features or fundamental points of struc- 

 ture which are common to the whole class, the following appear to me to present char- 



