180 PEOr. p. MAETIN DUNOAJSr ON THE 



but thab the interauricular parts were confounded witli the 

 border of the shell. The connection of the auricles of Echinus 

 with the ambulacra was both drawn and described. 



J. Miiller (Bau d. Echinodermen, Berlin Akad. 1854) gives a 

 most perfect figure of a Cidaris and describes the " auricles " 

 from that genus only. He figures the ambulacrum with the 

 projecting knobs seeu within the test on either side of the 

 median line, and terms them vertebral processes. Nothing can 

 be clearer than the fact so well illustrated by the great anato- 

 mist, that these " auricles " have no connection with the ambulacra 

 and that the ascending processes in Cidaris are interradial. 



It is evident that the " auricles " of ^c/wm^s noticed by Sharpey 

 are not homologous with the auricles of Cidaris as described by 

 Midler. 



Loven, in his wonderful ' Etudes,' p. 29, in treating of Cidaris, 

 states: — "La les auricules n'oflTrent pas de resistance. Eixees 

 par leurs bases exclusivement aus plaques interradiaires des deux 

 cotes de I'ambulacre," &c. 



Loven gave moreover the following very important description 

 of the " auricles " of other genera : — " L'existence d'un appareil 

 masticatoire puissant et tres-complique, pourvu de cinq pieces 

 d'appui, dites auricules, dont les bases elargies sont fixees par 

 soudure a la face interne des plaques peristomiennes et sub- 

 pcristomiennes du test, soit amiulacrales, soit interradiales, &c.' 

 The meaning of this refers to the difference in the position of 

 processes in Cidaris and the true auricles of all the other 

 Gnathostomes (Clypeastroids excluded) with which Loven was 

 cognizant. 



A. Agassiz, in the ' Eevision of the Echini,' 1872-74, p. 689, 

 states :■ — " In the Desmosticha, on the other hand, the jaws are 

 placed entirely within the line of the auricles, from which they 

 are supported by a very complicated set of muscular bands, 

 extending in pairs from the sides of the auricles, from their base 

 and from the intervening spaces, to different points of the 

 pyramid and of the braces," 



On the next page he writes : — "The auricles are interambulacral 

 processes : they are developed from the test itself, and do not 

 belong to the dental system as stated by Loven, while the teeth 

 and jaws are developed independently as isolated pieces in young 

 Echini. 



" In the Cidaridse the processes of the adjoining interambii- 



