p. H. CAEPENTEE ON" CEETACEOUS COMATUL^. 553 



Diameter 4| mm. 



Locality. The Upper Greensand, Blackdown. Collection of the 

 Eev. P. B. Brodie, M.A., F.G.S. 



Remarks. This is a very singular type, as it presents a com- 

 bination of several characters which are more or less distinctive 

 of various other Cretaceous species and of some recent ones. In 

 its general fades this fossil resembles the corresponding part of 

 A. celtica and A, Eschrichtii of the N'orth- Atlantic basin. The latter 

 species is the more like it, having a hemispherical centrodorsal with 

 a pentagonal outline and very similar articular faces, including the 

 enlargement of the ventral rim of the axial canal. The two types 

 differ, however, in points of detail, such as the lateral curvature of 

 the articular faces of A. incurva, so that the radials do not com- 

 pletely cover the centrodorsal ; and they show a small outer dorsal 

 surface, the flanks of which are upturned above the outer ends of 

 the basals. Both these characters are common to A. semiglohosa and 

 A, cequimarginata. In the former species, however, the upper 

 ends of the apposed lateral edges of the radials stand out more 

 prominently than in A. incurva ; while the articular faces of 

 A. cequimarginata have a very straight slope and lack the ventral 

 intermuscular notch which occurs in A. incurva, though the enlarge- 

 ment of the upper rim of the axial canal is common both to it and 

 to the recent A. Eschrichtii. 



The lateral curvature of the articular faces occurs in a new Pacific 

 Antedon (otherwise very different), in A. lenticularis, A. italica, and 

 in the so-called Hertha mystica * from the Cretaceous series of the 

 island of Riigen. There is a further resemblance to this last species 

 in the projection of the angles of the radial pentagon beyond the 

 margin of the centrodorsal, so that they are visible when the calyx 

 is viewed from below (fig. 1, b); but the ventral aspect of the 

 calyx is very different from that of Hertha, in which the articular 

 faces suddenly narrow very much near their ventral ends, while 

 Hagenow could discover no external basals, such as we find in 

 A. incurva. 



The close grouping of the cirrhus-sockets on the centrodorsal of 

 this species, and the faint stellate impression at its dorsal pole, give 

 it a certain resemblance to A. rotunda ; but its pentagonal shape is 

 sufficient to distinguish it, apart from other slight differences. 



In the following table (p. 554) I have endeavoured to show 

 the occurrence of characters belonging to this species in other 

 Comatulce. 



* Von Hagenow, " Monographic der Riigen'schen Kreide-Versteinerungen : 

 II. Abtheilung, Eadiarien und Annulaten," Neues Jahrb. f. Mineral. 1840, 

 p. 664. 



