40 C. M. Maplestone: 



complicated in structure. Tlie laminae first formed consist of 

 two single layers of zooecia, back to back, but subsequently 

 they are overgrown with other layers of zooecia, until the 

 laminae become thick and solid. All the laminae are j^erpen- 

 dicular to the base of the zoarium, and this disposition of 

 them is a constant feature, distinguishing the species from all 

 other flabellate massive forms. 



Zooecia elongate, oval ; surface granulated, with occasionally 

 a feAv pores, and with a few larger granulations or nodules round 

 the margin ; quite distinct and ventricose in those recently 

 formed, but in the older ones the front wall is more highly 

 calcified and the whole surface is raised, so that they appear 

 quite immersed and only partially defined by a few marginal 

 nodules, and the thyrostomes are in a depressed area. Thyros- 

 tomes subtri angular, distal angle rounded, proximal margin 

 slightly curved. Ooecia globose, surface granulated ; in the 

 centre of the front wall, above the aperture, is a large, long, 

 upright, elliptical area (sometimes slightly irregular in shape), 

 with a membranous covering ; ooecial opening and operculum 

 subtriangular. Locality, Spencer Gulf (the largest specimen 

 only), and Backstairs Passage, South Australia. 



As above stated, the zoaria are composed of vertical laminae; 

 the primary ones are generally three in number, and soon 

 branch off at various obtuse angles to one another ; the laminae 

 are flat or nearly so, and all, even the smallest, are perpendicular 

 to the base. In the simplest forms the laminae are few in 

 number. One specimen has only three, joined vertically in the 

 centre at an angle of about 120 degrees, it has developed no 

 additional laminae, but the zooecia have grown, layer upon 

 layer, until they are very thick. Dr. Hall has kindly photo- 

 graphed two of the specimens to illustrate this paper. The 

 largest one (PL VII.) is 9 inches long, (S inches wide, and 7 

 inches high, very solid and stony, some of the laminae being 

 nearly half an inch thick, and the base is two inches in diameter. 

 In the other specimen photographed (PI. VIII.), the laminae are 

 very numerous ; there are, counting great and small, no less than 

 40 distinct laminae on it, most of which are composed of only 

 two layers of zooecia ; the photograph is taken looking down 

 upon it, so as to show more clearly the disposition of the 

 laminae. 



