102 A MONOGRAPH OF THE TERTIARY POLYZOA OF VICTORIA. 



3. R. splnifera, n.sp. PL XII I., fig. 19. 



Zoarium encrusting. Zooecia broadly ovate or subcircular ; thyrostome large 

 with about eight spines on the upper margin, lower lip in young zooecia straight, in 

 older with a large process rising from one side and curved over towards the opposite, 

 which it nearly meets but leaves a narrow inclosed sinus ; in many zocecia on one 

 side of the thyrostome a round avicularium or vibracular pore on a slight eminence. 



M. 



Aspidostoma, Hincks. 



Zoarium bilaminate, expanded and foliaceous. Zocecia with the sides tumid, 

 especially in the upper part ; thyrostome at the summit of the zocecium, partly 

 concealed by the tumid border, arched above, straight below, and protected in front 

 by a broad, shield-like plate or mucro which is continued downwards for some 

 distance within the zocecium. 



1. A. crassum, Hincks. PL XIII., fig. 12. 



Aspidostoma crassum, Hincks, A.M.N. H., Peb., 1881 ; ? Eschara gigantea, 

 Busk, B.M.C., Pt. II., p. 91; A. gigcmteum, id., C.P., Pt. I., p. 161. 



Zoarium expanded, forming foliaceous expansions contracted towards the base. 

 Zocecia large, ovate or pyriform, separated by grooves, dense sides, especially above, 

 tumid, the front depressed below the thyrostome, but with a central tumid ridge 

 extending for a short distance downwards ; thyrostome arched above, straight below, 

 the lower edge with a broad squared plate, with a thickened margin extending to 

 the sides of the aperture, between which and the plate it forms a loop-shajjed notch. 

 Ocecia elongated, depressed and flat, minutely granular. 



W.P. Living between Patagonia and Falkland Islands (Hincks) ; Patagonia 

 and Tristan da Cunha (Busk). 



Hincks describes the margin of the hood-like border overarching the thyrostome 

 as rising into two pointed processes with a narrow cleft between. These are not 

 seen in my specimens, although in some of the zocecia there is a slight projection on 

 each side which probably represents them worn off. He also describes an avicu- 

 larium (absent in the fossils) leaning against the side of many of the zocecia a little 

 below the upper extremity. Otherwise the recent and fossil forms entirely agree. 

 Busk considered his own and Hincks' species as identical, but as that admits of some 

 doubt, I have retained the specific name given by Hincks. 



