Anatomical Novienclatare of Echinoderms. 21 



Agassiz, the plates generally known by this name being called 

 interambulacral throughout his fine work on the North 

 American Starfishes. Verrill used the same name for a while, 

 but afterwards abandoned it in favour of adambulacral, and 

 the same course was taken by Perrier. In a recent memoir 

 on the development of the calcareous plates of Asterias* 

 Fewkes describes the plates in question as interambulacrals, 

 with the remark, " adambulacrals of recent authors." The 

 name, however, is much older than Fewkes implies, having 

 been proposed by Miiller and adopted by M. Sars, Salter, and 

 Billings before 1860. Meek and Worthen and J. Hall used 

 it in 1866-67, and, with the exceptions above mentioned, I 

 know of no leading authority within the last twenty-five years 

 who liasused "interambulacral" todenote themarginal platesof 

 the ambulacra of the Starfish f. Fewkes says with regard to 

 them, " It iriay be as well to retain the old term, especially as 

 they arise between ends of successive ambulacrals" J. This, 

 however, is very far from being the real meaning of the old 

 term as applied to the Urchins, for which group it was first 

 employed. In a later communication again the two names 

 inter amhulacral and adamhulacral are used interchangeably 

 by Fewkes §, on the ground that " the term interambulacral 

 is not only the oldest, but is embryologically more accurate." 

 As, however, there are at least three series of plates in Star- 

 fishes to which the name interambulacral has been applied, it 

 would have conduced very considerably to the clearness of 

 Fewkes^s writings if he had followed the Miillerian plan of 

 describing one of them as adambulacral ; for when he speaks 

 of interambulacrals it is sometimes difficult to determine to 

 what series he is referring, and his use of the name for 

 Miiller's adambulacrals is the more likely to confuse, since his 

 studies have led him to believe that " they are the same as 

 the ambulacral " ||. The position of the plates in question is 

 not the less interambulacral because Miiller called them 

 adambulacral, to distinguish them from the other two sets of 

 interambulacral plates which are not so closely related to the 

 ambulacra. These are called marginals and inteibrachials 



* Bull. Mus. Comp. Zool. 1888, vol. xvii. p. 37. 



t They Lave beeu called adambulacrals by the following authors : — 

 Bell, Doderleiu, Eck, Fraas, Gaiioug, Ives, de Loriol, Liitken, Ludwig-, 

 Menegliini, S. A. Miller, Perrier, Rathbun, G. O. Sars, Studer, Sturtz, 

 Yerriil, Viguier, Zittel. 



t Bull. Mus. Comp. Zool. 1888, vol. xvii. p. 11. 



§ " On the Serial Relationship of the Ambulacral and Adambulacral 

 Calcareous Plates of the Starfishes," Proc. Boston Soc. Nat. Hist. 1889, 

 vol. xxiv. p. 96. 



II Proc. Boston Soc. Nat. Hist. 1889, vol. xxiv. p. 105. 



