or Little Known, Polyzoa. 291 



as calcification advances. In some specimens there are 

 numerous rounded avicularia scattered over the cells and 

 ovicells, occasionally raised on small elevations. There are 

 also other large avicularia with triangular mandibles, on 

 large mound-like elevations. 



Retepora fissa, M'G. Fig. 8. 



Polyzoary expanded. Fenestras narrower than the inter- 

 spaces. Cells separated by narrow raised lines ; mouth 

 rounded above, lower lip hollowed, entire, or with a loop- 

 shaped mark about the centre ; a considerable avicularium 

 with a triangular mandible near the middle of the cell, 

 directed downwards and outwards. Ovicells large, rounded, 

 prominent, with a vertical fissure wider above ; posterior 

 surface vibicate, slightly granular, with a few small avicu- 

 laria. 



Allied to R. cellulosa. The lower lip is usually 

 entire, although sometimes (as in the figure) with a small 

 loop-shaped mark or notch. The avicularium about the 

 middle of the cell varies in its direction, being usually 

 pointed obliquely outwards and downwards, sometimes 

 nearly transversely outwards, and occasionally slightly 

 upwards. It is sometimes very large, the rostrum much 

 elevated on a calcareous basis, and the mandible long and 

 triangular. 



Horner a robusta, n. sp. Fig. 1. 



Polyzoary composed of one or more thick, flattened stems, 

 from which lateral branches extend on either side, these 

 lateral branches frequently anastomosing with each other and 

 with those from adjacent stems. Cells arranged in numerous 

 longitudinal rows, separated by raised ridges ; mouth in 

 central cells slightly exserted ; in the lateral and those near 

 the edge the peristome produced and irregularly dentate. 

 Back of polyzoary longitudinally sulcate ; the narrow inter- 

 mediate ridges thickly punctate. OviceH large, posterior, 

 elongated in the direction of the branch, pitted. 



Port Phillip Heads. 



My largest specimen measures an inch and three-quarters 

 in height, and is of the same width at its broadest part. It 

 originates in a single stem, which immediately divides into 

 two, these again sub-dividing into several main branches. 



V2 



