TURBINARLE PELTIFORMES. 39 



Tlie process which brings about the early obliteration of the central polyp by the 

 cccnenchynie in young cups is often continued until the centre is convex. This leads 

 naturally (i. e. by the flow of the nutrient fluids along the canals towards the margin) to the 

 flat expansion of the stock as an encrusting mass. This method of growtli is exemplified by 

 several of the specimens in the Collection, notably by two magnificent almost circular stocks 

 4 to 5 feet across, retaining the original convex form hardly modified, exhibited in the 

 galleries. Tlie surface appears to die away in patches and to be grown over again. 



On the other hand, the cup shape may persist, though greatly disguised by folds. These 

 folds are very frequently of tlie bifrons type, i. e. they fuse back to back (PI. VII.). When 

 broken off, such folds appear as flat brandling fragments. Two such fragments are in tlie 

 Collection, one from Singapore. 



Some such branching fragments (? from China Seas) probably gave rise to Dr. Verrill's 

 species Turhinaria dichotorna* The description applies very well. The large number of 

 septa (50 to 60) might easily be obtained by counting the rudimentary septa which appear 

 between the 24 to 30 typically developed. 



A coral from Singapore, described by Ortmaun f under the name of T. 'maxima, is probably 

 also the same. 



There is a very large specimen forming an open slightly concave disc, from the surface 

 of which a few flat protuberances rise, which appears also to belong here, but as it had already 

 been labelled " T. patula," by Briiggemann, I have left it under that name. I have found it 

 difficult to draw any sharp line between T. peltata and T. imtula. In many cases, it seems 

 that the placing of specimens in one or the other group is quite arbitrary. 



The development of the ccenencliyma in tlie formation of these massive stocks 

 is sometimes so great that the polyps are all immersed, and individual stocks are found in 

 which the columella i.s not a continuous growtli, that is, the polyps must have become 

 detached from their columelhc in order to form new ones some millimetres above the old. In 

 such cases, the stages in the formation of the new columella as a proliferation of the edges of 

 the septa can be followed. 



A. Expanded like encrusting corals (Plate VIII.). 



a, h. King's Sound, North-West Australia. Saville-Kent Coll. 



c, d, c. Shark's Bay. Saville-Kent CoU. 



B. Cups persistent, but more or less disguised by folds (often bifrontal) (Plate VII.). 



ff. Singapore. ? 



h, i, j. Shark's Bay. SaviUe-Kent Coll. 



* 'Synopsis of Polyps and Corals,' Proceedings of the Essex Institute, vi. (1871) p. 89. 

 In addition to the claim embodied in Verrill's dichotomous species as to the existence of 

 branching Turbinarians, we have also Blainville's Gcmmipom ahrolanoidea, which he places under 

 the heading " arborescentes et partout cellulifores." This species of Gemmipore ( = TurbiimriaJ was 

 founded upon the Madrepora abroionoidea of Quoy and Gaimard ('Voyage de 1' Astrolabe,' iv. p. 232, 

 pi. xix. figs. 1, 2) ; itMs, however, not a Turbinarian at all, but apparently a. true Madrepore (vidf 

 ante, p. -1). 



t Zool. JB. Syst. Abth., iii. (1888) p. 160, pi. vi. fig. 4. 



