26 



The coraliite represented at Plate IV. Fig. 2, differs, in its figure, 

 from the other corallites of this species ; having somewhat of a 

 discoid appearance. This difference, I suspect, has depended entirely 

 on the a<re of the coral : the labours of the little modeller not 



o 



having been here so advanced as in those which have the turbinated 

 shape. In this specimen, the diameter of the disk more than equals 

 the height of the coral : the depth of the stellated cavity is therefore 

 necessarily small. The ra} 7 s pass from the centre of the cavity, and 

 terminate in the margin ; which appears to be preternaturally thick, 

 from its edge having probably been somewhat worn down, by rolling 

 on the shores of the Baltic, whence it was obtained. From the same 

 circumstance, perhaps, has proceeded the flatness of the stellated 

 surface ; the projecting parts of the radiating lamellae having been 

 also worn down. Sufficient, however, remains, not only to convey a 

 correct idea of the structure of the fossil, but to shew that it was a 

 dwelling exactly fitted for the accommodation of the animal described 

 by Donati, as the inhabitant of madrepores. 



By a careful inspection of many of these madreporites, I have 

 learnt, that they have been attached to the substance on which they 

 have grown, by tubes bearing the form, and so far performing to them 

 the office of roots, as to secure them from easy removal from their 

 native spot. This pedicle I consider as an essential part of these 

 animal substances ; and I trust, I shall be able to establish its exist- 

 ence sufficiently often, to warrant the assumption of its having existed 

 in all those bodies in which it cannot be directly manifested, but in 

 which its admission will render their nature much less difficult to un- 

 derstand. 



On the reverse, or inferior side of this fossil, longitudinal striae, 

 answering to the internal radiating laminae may be easily traced ; and 

 are intersected by distinct transverse ridges and grooves, marking the 

 progressive increase of the madrepore by the successive labours of its 



