206 DE. G. J. HTXDE ON SEPTASTE^A, d'oEBIGXY (1849), 



as shown in S. Forbesi and S. sexradiata, is b}^ buds, ^hich are 

 produced on the surface of the corallum in the interspaces between 

 the margins of the corallites. The commencement of this process 

 is clearlj' shown at and near the apex of the growing branches in 

 the type specimen of S. Foi^hesi ; on one branch of this example 

 there are ten distinct buds or young corallites (PI. IX. fig. 1 h). 

 At the interspace formed by the junction of fully developed coral- 

 lites there is first seen a smooth, shallow depression, bounded by a 

 slightly raised edge, about one third or one half the size of the 

 mature calices. At a further stage, slightly raised ridges, repre- 

 senting the septa, extend from the margins of this space towards its 

 centre. These incipient septa are irregularly developed ; in some 

 cases only four or five are present, and it is only exceptionally at 

 this early stage that a complete cycle of six septa makes its 

 appearance. The further growth of the young corallites can be 

 traced in the fractured ends of branches ; and the number and 

 disposition of the septa is very variable (PL IX. fig. 4). In the 

 course of growth, the corallites, near the apex of the branches, 

 follow a generally vertical direction in the axial portion of the 

 stem or branch for some distance, and they then curve and diverge 

 outwards until their calices are nearly at right angles to the axis. 

 Other corallites are very short and at right angles to the direction 

 of the stem throughout. Thus, in direct transverse fractures or 

 sections of the corallum, the corallites in the central portion are 

 seen in cross section, whilst near the margins their lateral walls or 

 longitudinal sections are exposed. The corallites appear to reach 

 their full width very rapidly. It is only on the surface of growing 

 or incipient branches that buds make their appearance. 



In all the examples of Septastrcea Forbesi and •S'. (Columnaria) 

 sexradiata which have come under my notice, there is not a single 

 decisive instance of increase by fissiparity to be met with, either on 

 the surface of the corallum or in the exi)osed fractured interior. It 

 is difficult to understand how these corals could have been described 

 as fissiparous. It is true that d'Orbigny does not, in the original 

 definition, mention the mode of increase ; but the genus Goniastrcea, 

 with which he compares Septastrcea, is a decidedly fissiparous genus, 

 though Prof. Duncan * states that gemmation occurs in it as well. 

 Edwards and Haimef, indeed, are not decisive as to this character, 

 but they frankly say that they had not determined the point, and 

 that it was possible that the corals, instead of being fissiparous, might 

 increase by submarginal buds, which is really the case. 



Prof. Duncan, however, in the ' Revision of the Madreporaria,' 

 p. 103, states, without qualification, that Septastrcea is character- 

 ized by " fissiparity of calices," and in Septastrcea Forbesi he finds X 

 that " fissiparity is exceptional, but occurs." But in a single spe- 

 cimen of S. Forbesi this author § figures from a fractured stem 



'■' Revision of the Madreporaria, p. 102. 

 t Ann. des Sci. Naturelles, 3^ ser. t. xii. p. 163. 

 I Quart. Journ. Geol. Soc. vol. xliii. p. 26. 

 § L. c. pi. iii. fig. 2. 



