4 DR. p. H. CARPENTER ON CERTAIN POINTS 



from the Caradoc beds of Montpellier. They are both dicyclie 

 and hesameroiis, though this is not the way in which Yon 

 Koenen interprets their structure *. The two genera resemble 

 one another and differ from Oaryocrinus in the absence of any 

 appendages on the third cycle of plates, or radials. In Garyo- 

 crinus the upper edges of these plates meet the peripheral plates 

 of the vault, the construction of which Avill be considered later. 

 But in Semicosmites there are no appendages round the margin 

 of the calyx, which contains another cycle of plates above the 

 radials. Miiller t has given a good descrijotion and figure of the 

 sis plates which bound the peristome and support the tbree 

 ambulacra proceeding from it (fig. I. on p. 22). I believe that 

 these plates reappear in Juglandocrinus (fig. III.)j a point to 

 which we shall return. 



Caryocystis granatum, as described by Von Buch %, also has a 

 j)roximal series of two large and two small plates, which I regard 

 as infrabasals. Above these come in succession three alternating 

 series of six plates each, basals, radials, and interradials (in the 

 widest sense of the term), and above these again are other plates, 

 somewhat irregularly disposed, which are probably mere indifferent 

 body-plates. 



Gottsche's interpretation of this tyj)e is a curious one§. He 

 regards the base as monocyclic, and five of the six plates in the 

 next ring as E', the odd one being an iuterradial, just as in 

 Semicosmites. Above these lie places five second radials, alto- 

 gether overlooking the fact that E," do not alternate with E' in 

 any Crinoid, so that any comparison which assumes this must be 

 altogether devoid of a morphological basis : and it is curious that 

 the very distinct hexamerous symmetry of this type should have 

 so entirely escaped Grottsche's notice. The form which is figured 

 in Augelin's ' Iconographia '|| under the name oi Caryocystis testu- 

 cUnaria is pentamerous, while C. alutacea, Angeliu, and C. pro- 

 minens, Angelin, seem to be tetramerous. In like manner some 

 forms of Protocrinus oviformis are distinctly dicyclie and hexa- 

 merous, while others are more irregular and indicate a divergence 



* " Ueber neiie Cystideen aus den Caradoc-Schichten der Glegend von Mont- 

 pellier," Neues Jahrb. f. Min. 1886, Bd. ii. pp. 249-254. 



t " Ueber den Ban der Echinodermen," Abhandl. d. k. Akad. d.Wiss. Berlhi, 

 1853, Taf. vi. fig. 5. 



+ hoc. cit. pp. 17, 18, Taf. ii. fig. 4. § Loc. cit. p. 13. 



II ' Iconographia Crinoideorum,' 1878, tab. xiii. fig. 8. 



