REPORT ON THE CRINOIDEA. 169 
T regard the inner ring of interradial dome plates (proximals) in the Actinocrinidee 
and Platycrinide as representing the orals of a Neocrinoid, or of Symbathocrinus, 
Haplocrinus, and the young Allagecrinus. This view was first suggested in 1879,’ and 
all that has since been written on the subject by Wachsmuth and Springer, who have 
not discussed it in any way, has only served to make me more confident of its truth. 
In the first place, Wachsmuth himself has recognised from paleeontological evidence 
the close similarity between the proximal interradial plates of the actinal and abactinal 
systems respectively. Those of the abactinal system are the basals, which in Actino- 
erinus and Cyathocrinus “develop very early in the young, and attain almost their full 
Taste VII.—Showing the Mutual Homologies of the Principal Plates in the Actinal 
and Abactinal Systems of Echinodermata. 
Urchins. Ophiurids. Crinoids. 
Actinal. 
Abactinal. Abactinal. Actinal. Abactinal. 
Symbathocrinus. | Actinocrinus. 
1. | Central plate. Dorsocentral. | Dorsocentral. Terminal plate Orocentral. Orocentral. 
at base of 
larval stem. 
2. | First series, Under-basals, Under-basals, 
radial. (variable). (variable). 
3. | Second series, Genitals. Basals. Mouth-shields. Basals. Orals. Proximal dome 
interradial. plates. 
4. | Third series, Oculars. Radials. Primary calyx Primary dome 
radial. radials. radials. 
Orders of calyx Orders of dome 
radials, radials, 
Calyx interra- Dome _ interra- 
dials. dials. 
No representatives of the under-basals have been detected as yet in the apical system of an 
Urchin, nor in the oral (or actinal) system of any Echinoderm. 
size when even the first radials are comparatively much smaller.”* This is also true of 
the basals of recent Comatule, and of the orals as well; while in like manner the 
proximal dome plates of Actinocrinus are relatively largest in young individuals. 
Goette’s observations show the complete homology between the basals and orals, both 
being developed spirally, the former round the right, and the latter round the left 
peritoneal tube. The basals are primitively next to the abactinal centre in Urchins and 
Stellerids, and are only removed from it in the Crinoid by the growing stem; while the 
orals are next the actinal centre, no plate being developed there, however, in the recent 
1 Quart. Journ. Micr. Sci., 1879, vol. xix., N. S., p. 179. 
(ZOOL. CHALL, EXP.—PART XXx11.—1884.) 
2 Revision, part i. p. 20. 
li 22 
