26 Thomson, South African dor gon-.icca. 



mous, the other not so regular. The verticils are closer to one 

 another near the apices than basally ; generally 5 verticils 

 occur in a length of 15 millimetres. A point about some of 

 the verticils is that they do not run straight round the axis, 

 but in an irregular or slightly spiral manner. The coenenchyme 

 between the lower verticils, and covering the basal stem, has 

 scale-like spicules of varying shape and size, which fit closely 

 into one another; some of the larger are I millimetre in length. 

 The base of the colony is large, namely, 8 mm. in height and 

 diameter. An interval of about a millimetre occurs between 

 the lower verticils, the upper verticils being closer to one another. 



The larger ])olyps are about 3 mm. in height, and 1.75 mm. 

 in diameter. The body or dorsal surface is enveloped by three 

 series of paired scale-like spicules, which overlap one another. 

 The two ad-axials are thick, and hollowed out to form a hood- 

 like part, those of right and left sides form a deep median, 

 wavy, slightly oblique groove, where they meet one another. 

 The median pair of sclerites is smaller, partly hidden by the 

 ad-axials, and their outer borders are slightly sinuous but entire. 

 The ab-axial pair is longer than the last, each sclerite slightly 

 overlaps the other in the median line, and has an entire but 

 slightly wavy margin, sometimes in contact with the polyp 

 lying basal to it. The ad-axials only connect latcrallv with 

 those of the polyps on either side. There are no sharp projec- 

 tions or spines on any of those sclerites. The exposed parts of 

 the ad-axials are about 1.2, of the medials .75, of the ab-axials 

 I.I mm. in length. These three pairs of plates correspond to 

 the basal, medial, and buccal sclerites of Versluys. At the 

 base of the polyp, and partly hidden by the ab-axials, are the 

 opercular spicules, which are generally seven in number, and 

 have frequently a wa\y semi-triangular appearance; in some 

 cases they almost come in contact with the upper spicules of 

 the polyp beneath, but do not project beyond the ab-axial 

 sclerites to any extent. The sclerites of the inner or ventral 

 surface of the polyp and surrounding the axis are large, thick, 

 and stone-like, they are very hard, and differ considerably in 

 size. In one verticil of 8 polyps, 21 of these sclerites lay sur- 

 rounding the axis. This layer of spicules is sometimes i mm. 

 in thickness, and has i or 2 spicules at any one place, counting 

 in a transverse direction. 



The spicules of the coenenchyme near the base form a 

 well-marked layer, a little less than a millimetre in thickness. 

 1 hey differ in shape and size, being quadrilateral, oval, pear- 

 shaped, etc. and ranging from about 0.270 x 0.234 to 0.720 x 

 0.576mm. At some parts they slightly overlap one another, 

 at others there is a space on one side between them. The 

 sclerites from the coenenchyme between the verticils are some- 

 what similar to the last, but are slightly more irregular, and 

 more frequently with spaces between them ; they range in size 

 from about 0.270 x 0.324 to o.go x 0.54 mm. The opercular 



