56 



THE CRAG POLYZOA. 



The species comprised in the genus Cellepora, defined as above, fall very naturally 

 into two groups, which are distinct in habit and general appearance, though very closely 

 alike in their internal constitution. 



1. One of these groups, corresponding with the Beptocelleporaria of D'Orbigny, 

 contains those species whose polyzoaries are adnate and incrusting, assuming more 

 or less of a globose form, or that of thick, irregular, bossy masses, often of considerable 

 size, though sometimes very minute. This group may be typified by the common 

 C. pumicosa of our seas. The other subdivision embraces those species which affect an 

 erect ramose mode of growth, consisting of a stem and irregularly dichotomous, tapering 

 branches. These may be represented by Cellepora ramulosu. 



Owing lo the confused mode of growth of the polyzoarium in Cellepora, and the 

 extreme diversities exhibited by the cells in different parts of one and the same specimen, 

 it is in many cases difficult, even in recent species, to determine the true characters of any 

 given fragment. In the case of fossils this difficulty is of course very greatly increased, 

 and I have consequently found it almost impossible to assign positive characters in a great 

 mony instances. The definitions and distinctions of species here given must therefore be 

 accepted with great hesitation, and regarded simply as the results of the best consideration 

 of the subject the condition of the specimens has allowed. 



SYNOPSIS OF SPECIES OF CELLEPORA. 



1. Ramose, suberect. 



1. C. coronopus 



2. C. ramulosa . 



3. C. compressn 



4. C. eespitosa 



p. 57, Pi. IX, figs. 1 and 3. 

 p. 58, PI. IX, fig. 2. 

 p. 58, PL IX, fig. 4. 

 p. 59, PL IX, fig. 5. 



2. Aduate, incrusting, massive. 



5. C. edax 



6. C. tubigera . 



7. C. scruposa 



8. C. parasitica 



9. C. dentata . 



p. 59, PL IX, fig. 6. ; PL XXII, fig. 3. 



p. 60, PL IX, figs. 8 and 10. 



p. 61, PL IX, fig. 9. 



p. 61, PL IX, figs. 11 and 13. 



p. 62, PL IX, fig. 12. 



