Anatomical Nomenclature 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, u 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 has used u interambulacral” to denote the marginal plates of 
the ambulacra of the Starfish f. Fewkes says with regard to 
them, u It may 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 
interambulacral and adambulacral are used interchangeably 
by Fewkes §, on the ground that u 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 Mullerian 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 
Muller’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 Muller 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 interbrachials 
* Bull. Mus. Comp. Zool. 1888, vol. xvii. p. 37. 
t They have been called adambulacrals by the following authors : — 
Bell, Doderlein, Eck, Fraas, Ganong, Ives, de Loriol, Liitken, Ludwig, 
Meneghini, S. A. Miller, Perrier, Bathbun, G. O. Sars, Studer, Sturtz, 
Verrill, Viguier, Zittel. 
X Bull. Mus. Comp. Zodl. 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. 
|| Proc. Boston Soc. Nat. Hist. 1889, vol. xxiv. p. 105. 
