1848.] LONSDALE ON FOSSIL ZOOPHYTES. 89 



structural development. All the interpolations of Cyathophora ? 

 elegans clearly originated in the hemispherical or radiating mode of 

 growth, by which greater interspaces were produced than accorded 

 with the ordinary range of the cellated lamellse. At the incipient 

 points that structure apparently ceased to be formed continuously, 

 and a small area was the result, surrounded by the edges of a very 

 limited number of parted lamellae. Even in this earliest state, 

 therefore, the essential parts of a cavity existed, and could be 

 supported without the aid of a new digestive apparatus, the com- 

 ponent structures being portions of the adjacent mature hollows 

 and nourished by them. As the old lamellse extended upwards, the 

 young receptacle deepened and widened, and became fit to contain its 

 own alimentary organs, and thereby add to the framework. This 

 manner of production explains why some lamellse may extend com- 

 pletely between two adjacent cavities, and the remainder have only 

 a limited range. In Siderastrcea galaxea the interpolating process 

 is modified in conformity with the peculiarities of the coral. The 

 mature abdominal hollows are separated by somewhat broad and 

 raised interspaces, and the first signs of an additional one is a shallow 

 depression, due apparently to a suspension of calcareous secretions. 

 In that state no new laminae are ■^'isible ; the bottom and sides of the 

 little concave area being composed of smooth plates and transverse bars 

 belonging to the quadrangular network ; but in a slightly advanced 

 stage, finely attenuated additions had been made to the edges of the 

 former, so far as they bordered the sides of the cavity, whereby they 

 assumed a decidedly lamellated character ; while in other cases, which 

 exhibited a little further progress, similar plates had acquired the 

 form and disposition of converging lamellae, with a small central 

 axis ; the young hollow resembling a diminutive mature one ; and 

 the early perfecting of the star accords with the general structure of 

 the coral. Another mode adapted to the peculiarities of the case is 

 exhibited by a polyparium resembling Ellis and Solander's figure 

 oi Asti'cea pleiades (tab. 53. fig. 7, 8), but which does not strictly 

 coincide with the descriptions of that species, or any other known to 

 the author of these memoranda. The interspaces however are more 

 or less concave, and traversed by outward extensions of the lamellae, 

 generally attenuated, and often curved ; they occasionally present 

 also distinct, prominent papillae, and the base is an apparently con- 

 tinuous solid plate. In this case, the bottom of the interval being 

 below the margin of the stars, no preparatory depression was requi- 

 site ; and the first indication of an incipient cavity is an irregular 

 convergence of thin laminae, issuing from the edges of the old lamellae, 

 with the addition of others similarly slender ; the whole uniting 

 in the middle of the area and presenting an imperfect star : a little 

 more advanced state has rays of greater regularity, a decidedly reti- 

 culated centre, and a projecting circular boundary ; or it exhibits a 

 completely formed, small visceral receptacle. In tins coral, as in the 

 preceding, the lamellae occupy to a great extent the interior of the 

 cavity, and are therefore primarily developed ; no particular depres- 

 sion however is prepared, but a boundary is constructed ; the former 



