APPENDIX. 
NOTE A. 
(Pages 2, 157, and 168.) 
On THE HoMoLoGIEs OF THE CRINOIDAL CALYX IN THE OTHER ECHINODERMS. 
Tue relations of the plates which enter into the composition of the calyx of a Crmoid 
to those constituting the apical system of an Urchin or a Starfish are still the subject of 
much discussion. 
The apical system of an Urchin, as described by Lovén,* consists typically of a dorso- 
central plate enclosed within two rings of five plates each. The plates of the proximal 
ring (genitals, Auct.) are interradial in position, while those of the outer ring (oculars) are 
radially situated. Believing that the dorsocentral is represented in the Pentacrinoid 
larva of a Comatula by the terminal plate at the base of the stem,” I have suggested that 
the basals of the Pentacrinoid are homologous with the so called genitals of an Urchin ; 
while the ocular plates of the latter correspond to the radials of the Crinoid. So far as the 
basals and radials are concerned this view is fundamentally the same as that previously 
expressed by Lovén and Agassiz, allowance being made for the difference between their 
terminology and that employed by myself; so that the homology between the basals and 
radials of a Crinoid and the two rows of plates surrounding the dorsocentral of an 
Urchin has been pretty generally accepted. 
Dr. R. Hoernes,? however, objects to this homology (which he associates with my 
name) on the ground that the resemblance should be most marked in the geologically 
oldest types, “ was keineswegs der Fall ist, da gerade der Scheitelapparat der Palaechinoiden 
durchaus nicht an die Basis-Entwickelung der Crinoiden-Kelches sich anschliesst.” 
This objection may be answered in two ways. 1. Lovén* says that the general formula 
of the apical system of Echinoidea “ has remained, more or less altered, but always recognis- 
able, from Palaeozoic to recent time.” 2. The positive fact that the basals and radials of 
1 Etudes sur les Echinoidées, K. Svensk. Vetensk. Akad. Handl., Bd. xi., 1874, No. 7, p. 65. 
2 Quart. Journ. Mier. Sci., 1878, vol. xviii., N. 8., p. 3874. 
3 Blemente der Palzontologie (Palwozoologie), Leipzig, 1884, p. 130. 
4 On Pourtalesia, a genus of Echinoidea, K. Svensk. Vetensk. Akad. Handl., Bd. xix., 1883, No. 7, p. 62. 
(zooL. CHALL. EXP,—PART xxxu,—1884.) ii 50 
