118 Proceedings of the Royal Irish Academy. 



from Mauritius, giving some positive, additional characters. One of his 

 specimens was 340 mm. in height, and 240 mm. in maximum diameter. He 

 says : — " The shape of the verrucae varies considerably according as to 

 whether they are open or closed ; in the former conditiou they are rectangular 

 at the apex, while in the latter they appear conical with rounded apices. 

 The basal diameter may vary from V2b mm. to 2'25 mm. when closed. The 

 spicules consist of a dense cortical layer of small double-heads and a sub- 

 jacent layer of longer densely tiiberculate spindles having a bare median 

 space more or less strongly indicated. The colour is variable, (1) ochreous 

 yellow to a dull flesh colour, (2) dirty white." 



In 1897 Whitelegge established a new species under the name Nieella 

 laxa with the following characters : — The colony is feebly branched ; the 

 branching is lateral and in one plane. The axis is laminate and calcareous. 

 The coenenchyma is thin, and when viewed with a lens presents a series of 

 minute ridges, forming a network of raised lines, which are lighter in colour 

 and consist of double-club spicules. The polyps are confined to the sides of 

 the stem and branches in a single row on each side. The verrucae are large, 

 alternate, and stand nearly at right angles ; they are divided at the summit 

 into eight lobes. The spicules consist of (1) short double-clubs with smooth 

 or warty tubercles: 01 X 0-05 mm.; O'OV X 0-03 mm.; 0-05 x 0-02 mm.; 

 (2) fusiform spindles with rather obtusely pointed ends and a spiny tuber- 

 culated surface : 0-25 x 0-06 mm.; 0-2 x 0-05 mm.; 01 x 0-03 mm. Many 

 of both kinds are a little flattened. The colour is a light mouse-grey. 



He says: — "This species differs from N. dichotoma by its smaller and 

 more distant polyps and by its lax method of branching." 



We have already seen that neither of these two characters is of much 

 taxonomic importance ; and, taking into consideration Eidley's observations on 

 the size of verrucae in diflerent stages of retraction, we do not feel justified 

 in ranking this as a distinct species. At the same time Gray gives a very 

 good figure of his N. mav.ritiana, and the branching there is almost identical 

 with that figured by "Whitelegge. In Gray's figure also the distribution of the 

 polyps varies in different parts of the colony, so that while in some branches 

 they are more closely packed, in others they are quite as distant as in 

 Whitelegge's figure. The spicules are identical with those described by 

 Eidley ; and the network of ridges described by Whitelegge, though not given 

 in Gray's description, are unmistakably present in his figure. We therefore 

 see no reason for rarking N. laxa as a separate species. 



Thomson and Eussell, 1909 (xliii., p. 161, Plate vii., figs. 1 and 5) describe 

 some specimens as follows : — 



Several colonies of chestnut-browu to umber-brown colour. The largest is 



