PENISATTTLIDA OF THE MERGUI AECHIPELAGO. 



281 



Section IV. Veeetillej. 

 Family i. Caveenulaeiid^;. 

 Grenus Caveeisulaeia, Valenciennes. 



Cayeexttlaeia obesa, Vol. (Plate XXIII. fig. 18.) 



Of this variable species there are twelve specimens in the col- 

 lection, all from the Andaman Islands. 



The majority of these agree in all respects with the descrip- 

 tion given by Kolliker * ; two specimens, however, present special 

 characters, and may be described as a distinct variety. 



Cav. obesa, var. a. 



The two specimens in question, while agreeing in all essen- 

 tial respects with the typical form, are characterized by their 

 very irregular shape. In one the stalk is absent, apparently 

 cut off by the dredge. The rachis is cylindrical and of nearly 

 uniform diameter in its lower three-fourths ; the upper fourth 

 is much narrower, and is separated by a marked constriction 

 from the lower part, from which it projects somewhat obliquely 

 as an irregular finger-like process. 



The second specimen, which is drawn the natural size in fig. 18, 

 is complete. The stalk is very short ; the rachis, which is rather 

 flabby in texture, expands from below upwards, and is produced 

 at one side into a rounded terminal knob or bud. This knob 

 appears to be the seat of most active growth, inasmuch as on 

 it the polypes are smaller and much closer together than in 

 other parts. The whole of the surface of the rachis between the 

 polypes is covered, as usual in this species, with minute siphono- 

 zooids. 



This irregular mode of growth, curiously like the budding of 

 Alcyonium, is probably to be associated with the absence, in 

 Cavernularia obesa, of the calcareous axis usually found in 

 Pennatulida. 



For the sake of comparison we give the principal measurements 

 of some of the specimens, including those of the second example 

 of var. a. 



* Kolliker, op. cit. pp. 338-343, and pi. xxii. figs. 199-201. 



