.METOPASTER PARKINSONI. 61 



tions for the articulation of setae. Supero-marginal plates ordinarily few in 

 number, and form a broad border to the disk. Ultimate paired supero-marginal 

 plates the largest of the series. Abactinal area covered with polygonal, and 

 usually hexagonal, plates (some of which may have stellate bases), and upon the 

 tabulae are borne small, more or less co-ordinated granules. Infero-marginal 

 plates more numerous than the supero-marginal series, and decreasing in size as 

 they approach the extremity of the ray. Their ornamentation similar to that of 

 the superior series. Actinal intermediate plates small, polygonal, covered with 

 uniform granules. Armature of the adambulacral plates arranged in lonoritudinal 

 lines. Small entrenched pedicellarias may be present occasionally on the plates. 



Metopaster differs from Pentagonaster by the large ultimate paired supero- 

 marginal plates, by the comparatively small number of the supero-marginal plates, 

 which are also fewer in number than the infero-marginal series, and by the 

 character of the ornamentation of the marginal plates of both series. 



The forms ranked under this genus were all classed by the late Professor 

 Edward Forbes under Goniodiscus, which he considered to be a sub-o-enus of 

 Goniaster. There is, however, no justification whatever in my opinion for regard- 

 ing any of the Cretaceous starfishes hitherto described as belonging to either the 

 genus Goniaster or Goniodiscus. The species which may be considered as the types 

 of each of these genera are existing forms, and no Cretaceous forms agreeing in 

 structural detail have, so far as I am aware, been discovered. It is also erroneous 

 to rank Goniodiscus as a sub-genus of Goniaster. The two genera belong to 

 different families ; and I am in perfect accord with Professor Edmond Perrier as 

 to the limitation of the two genera. His view appears to me to be perfectly 

 logical, and to be the result of careful and impartial judgment. I also consider 

 that the fossil forms under consideration are quite distinct from the recent genus 

 Astrogonixim, as limited by me elsewhere.^ 



1. Metopastee Paekinsoni, Forbes, sp. PI. IX, figs. 2 a— 2 c ; PI. X, figs. 1 a— 



5 c ; PI. XI, figs. 1 a— 2 c ; PI. XII, 

 figs. 1 a— I d ; PI. XVI, figs. 2 a, 2 b. 



Pentagonastee EEGULAEI8, Parkinson, 1811. Organic Reniaius, vol. iii, p. 3, pi. i, 



fig. 3 (non Linck). 

 TOBIA EEQULAEis, Morris, 1843. Catalogue of British Fossils, p. 60. 



1 < 



Zool. Chall. Exped.,' part li, "Eeport ou the Asteroidea," 1889, p. 285. 



