SiMi'SMN — A Revision of the Govfjonellidae. 367 



furrows, which are sinuous, and sometimes ahnosl spirally twisted ; one being 

 generally deeper than the others. These extend into the secondary branches, 

 and even into one side of the twigs, tlie number diminishing with the size of 

 the branches. 



The axis is very calcareous and cylindrical in form. It is composed of 

 concentric laminae, and has an almost olive-green colour at the base, gradually 

 merging into a pale yellow in the smaller branches. 



The polyps are disposed essentially in two longitudinal series; but 

 deviations occur in several places, due sometimes to the anastomosis and 

 sometimes to overcrowding. They are chiefly lateral on the main stem or 

 primary branches ; in the secondary branches they are arranged almost all 

 round. On the finer branches and twigs they occur for the most part on two 

 sides ; but this rule is broken occasionally by the occurrence of polyps on all 

 the four sides. The verrucae are dome-like, but slightly flattened on the 

 twigs. They are separated by intervals of about 1 mm. in the branches ; but 

 their bases touch on the branchlets and give an undulating appearance. 

 They measure about 0'5 mm. in height and 1 mm. in diameter. Wlien the 

 verruca closes over the retracted polyp, an eight-rayed star is formed by the 

 eight lobes of the wall. The anthocodiae are very minute and are completely 

 retractile ; the spicules are arranged transversely on the tentacles. 



The spicules of the coenenchyma consist of small double-clubs, elongated 

 double-clubs, double-spindles, and simple-spindles. The double-spindles and 

 simple-spindles in this species are not so markedly disproportionate as in 

 most other species ; but their distinctive character justifies their inclusion in 

 the genus Nicella. 



The following are a few of the more common types, with measurements 

 in millimetres : — 



(«) Double-clubs, with smooth warts : 



0-05 X 0-04 ; constriction 0-02 broad x O'OOS long. 



0'048 X 0-04 „ 0-02 „ x O-OOo „ 



(h) Elongated double-clubs, with fewer and more irregular warts : 



0-06 X 0-04 ; constriction 0-03 broad X 0-01 long. 



0-048 X 0-035 „ 0-02 „ x 0-012 „ 



(c) Spindles with round warts, and double spindles, having a smooth part 

 in the middle : 



0-09 X 0-025 ; smooth part, 0-02 long. 



0-085 X 0-028 „ „ 0-018 „ 



{d) Minute crosses, with a very distinct cross, 0-04 X 0-04. 

 (c) Minute irregular crosses, elongated along one diagonal, with distinct 

 cross, 0-05 X O-O:^. 



R.I. A. PROC, VOL. XXVIII., SECT. B. [3 C] 



