MAY 9 1903 



Descriptions of Ne^w Species of Corals 

 FROM THE Australian Tertiaries. 



By J. Dennant, F.G.S. 



PART IV. 



Plate I. 



[Read November 5, 1901.] 



Four species, distributed among the same number of genera, 

 are discussed in this part. I am unable to place the first species 

 described in any existing genus, and the following new one is 

 instituted for its reception. It is perhaps nearest to Dasmia, 

 Edw. and Haime, but is without the threefold division of the 

 septa assigned to that genus ; moreover, the cyclical arrangement 

 is peculiar. 



Genus Holcotrochus, nov. 



Corallum free, compressed. Septa ten, in one cycle, and 

 abnormal in development. 



Costse corresponding to septa, broad, equal, and separated by 

 deep grooves. Columella parietal. No epitheca. 



HolCOtPOehUS SCriptUS, spec. nov. PI. i., figs, la, h. 



Corallum cuneiform, with roundly-pointed base. Calice ellip 

 tical, the ratio of its major and minor axes being as 100 to 57. 



The costie form the most marked feature of this curious coral. 

 Only ten are present, and they are equal in size, very prominent, 

 broad at the top, and regularly tapering at the base, where thev 

 unite. Of these ten there is one at either end, and four on each 

 of the broad surfaces of the corallum. All are ornamented 

 laterally by a regular series of closely-set incisions or scribed 

 markings at right angles to their length. A slender and some- 

 what sinuous rod-like process, mostly granular, but occasionally 

 plain, in each of the deeply-grooved interspaces, extends from ihe 

 calicular margin to the base, and serves to connect adjoining 

 costse. The costse themselves and these slender rods form in fact 

 the only wall of the corallum. 



The septa, also ten in number, are continuations of the costee, 

 and rise perpendicularly from them to about one-sixth of the whole 

 height of the corallum, when they bend sharply round towards 

 the central fossa, the upper surfaces of all being horizontal and 

 on the same level; they are coarsely granular on their sides, plain 



