REPORT ON THE CRINOIDEA. 



169 



I regard the inner ring of interradial dome plates (proximals) in the Actinocrinidae 

 and PLatycrinidse 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 palseontological 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- 

 crinus and Cyathocrinus " develop very early in the young, and attain almost their full 



Table VII. — Shoiving the Mutual Homologies of the Princiiml Plates m the Actinal 

 and Abactinal Systems of Echinodermata. 



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 Comatulae, 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. Joimi. Micr. Sci., 1879, vol. xix., N. S., p. 179. 

 (ZOOL. CHALL. EXP. — PART XXXH. — 1884.) 



2 Revision, part i. p. 20. 

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