4 
Dr. P. H. Carpenter on the 
central plate of the Echinoderm apical system has been 
repeatedly noticed by ns both and also by others under the 
name u dorsocentral ; ” and zoologists have been warned 
again and again not to confuse it with the enlarged top stem- 
joint in the stem of many Crinoids, for which, in the case of 
Comatula , Miiller and his successors had employed the name 
u centro-dorsal.” Early in 1887 Duncan and Sladen *, 
writing on the morphology of the Saleniidae, frequently re- 
ferred to the so-called sur-anal plate of Echinids as the dorso- 
central, mentioning at the same time its homologies in the 
Asterids and Ophiurids. Fewkesf, who had previously 
confounded dorsocentral and centro-dorsal, wrote a short time 
later in the same terms. But all our efforts to obtain a greater 
precision of nomenclature seem to have been in vain, for even 
such a well-informed writer as the late Professor Neumayr { 
alluded in 1888 to u die centrodorsale Platte bei Salenien.” 
Unaware, too, that the presence of independent under-basals in 
the Antedon-\&YY& had been announced by Bury § in 1887, he 
concluded that they are represented by the u centrale Platte,” 
by which he meant the enlarged top stem-joint or centro- 
dorsal. But as he also recognized the fact that these under- 
basals are well developed in Marsupites and enclose u eine 
grosse centrodorsale Tafel,” he was driven to the following 
conclusions || : — 16 Es scheint demnach, als ob die centro- 
dorsale Platte der ausgewachsenen Crinoiden durchaus nicht 
immer dieselbe morphologische Bedeutung hatte, und auch 
durchaus nicht nothwendig immer dem gleichnamigen Theile 
der Antedon- Larve entsprache.” But is it so certain that the 
central plate in the calyx of Marsupites should be called a 
centro-dorsal at all, i. e . that it is an enlarged top stem-joint ? 
Twelve years ago I gave reasons for believing it to be a 
primitively imperforate plate homologous with the dorso- 
central of Salenia , and not a top stem-joint with its central 
canal obscured by a secondary calcareous deposit ^f. My 
arguments have never been refuted ; but palaeontologists have 
nevertheless continued to speak of the centro-dorsal of Mar - 
* (l On some Points in the Morphology and Classification of the 
Saleniidae, Agassiz/ Ann. & Mag. Nat. Hist. 1887, ser. 5, vol. xix. pp. 119, 
t Bull. Mus. Comp. Zool. 1888, vol. xvii. p. 38. 
X ‘ Die Stamme cles Thierreichs/ Wien, 1889, Bd. i. p. 493. 
§ “ The Early Stages in the Development of Antedon rosacea ,” Deport 
of the Fifty-seventh Meeting of the British Association, held at Man- 
chester, 1887 : London, 1888, p. 735. Also Proc. Roy. Soc. 1887-88, 
vol. xliii. p. 299. 
I| Op. cit. p. 493. 
IT Quart. Journ. Micr. Sci. 1878, vol. xviii. pp. 380, 381. 
