UPPER, OR FLINTY CHALK. 161 



zontal dissepiments. The cells are distinct and obscurely hexagonal, and 

 the partitions simple, as in Madrepora retepora of Ellis *; their cavities are 

 filled with chalk. 



Alcyonium. 



To this genus the fossil remains of zoophytes of very dissimilar cha- 

 racters have been referred by oryctologists. These bodies, whether convex 

 or concave, soUd or porous, simple or ramose, possessing a pedicle, or 

 destitute of processes of attachment, appear to have been indiscriminately 

 named alcyonia, whenever their relation to other estabhshed genera was 

 not very manifest. But if we restrict the term to the fossils that agree 

 with the Linnean definition f, and assume the A. digitatum as the type of 

 the genus, the number of those which are found in a fossil state will be 

 comparatively small. And when it is considered, that even many recent 

 species are with difficulty distinguished from the spongice and other 

 analogous zoophytes, it will not appear surprising, if in numerous in- 

 stances the generic characters of the fossils in question, cannot be accu- 

 rately determined. In this place, we shall therefore describe as alcyonia, 

 those specimens which either in form or structure, bear even a remote 

 resemblance to the recent species of the genus. 



7. Turbinated alcyonite. Tab. xv. fig. 5. 



This fossil is of an inversely conical figure, the upper part being 

 slio-htly convex, and having a shallow circular cavity in the centre. The 

 external surface is marked with several reniform depressions, but is 

 destitute of the porous structure observable in the recent alcyonia. The 

 constituent substance is chalk. 



This specimen corresponds in many respects, with the "siliceous 

 alcyonite," described by Mr. Parkinson, {Org. Rem. Vol. ii. Tab. ix. 

 fig. 6.) 



* Ellis' Zoophytes, Tab. liv. fig. 3. . i t • r n 



t Alcyonium. Gen. Char. Body fleshy, gelatinous, or spongy ; with an external skin full 

 of openings, possessed by oviparous tentaculated hydrae ; the stirps fixed. 



