DOMOPORA TRUNCATA. 



DOMOPORA TRUNCATA, JamCSOU. 

 Plate LXIII. figs. 5-9. 



MILLEPORA TRUNCATA, Jameson, Wern. Mem. i. 560. 



Ti'urupORA TRUHCATA, Johnst. (part.), B. Z. ed. 2, 271, pi. xxxiii. figs. 8- 



10 (not good). 

 DOMOPORA TRCNCATA, Peach, Journ. Linn. Soc., Zool. xiii. 483. (Not Tubu- 



lipora truncate, Fleming, nor De/rancia truncata, Busk, 



Annals, ser. 2, iviii.) 



Zoarium mammiform, with an adherent, expanded, cir- 

 cular base, white ; surface porous, sometimes simple, 

 sometimes proliferous, and consisting of a cluster of 

 the mamillated disks, the top rounded and furrowed. 

 Zocecia disposed in very slightly elevated multiserial 

 rows, varying in number, separated by very shallow 

 grooves, which originate at the base of the rounded top 

 and radiate towards the summit. 



Height not exceeding inch, usually less. 



THIS species varies much in different stages and condi- 

 tions of growth. In its young state it consists of a more 

 or less circular adherent disk, with a cellular border, 

 sloping a little outwards, very slightly elevated in the 

 centre, towards which a number of indistinct rays, ori- 

 ginating on the inner edge of the border, converge. The 

 whole surface is porous ; but the zooecia are aggregated 

 on the radiating rows. In this stage there is the merest 

 rudiment of the central, somewhat dome-shaped rising 

 which is characteristic of the adult, and the zoarium very 

 closely resembles a Lichenopora. The mamillary elevation 

 seems to be formed by successive growths, superimposed 

 one upon another. Frequently the expanded base bears 

 a group of several mamillae, which are sometimes united 

 in pairs ; in one case six are joined together in one com- 

 posite colony, each of the buds developed on the discoid 



