A MONOGRAPH OP THE TERTIARY POLTZOA OF VICTORIA. 97 



avicularmm on the outer side close to the thyrostorne, the mandible pointed 

 downwards and inwards, the sides much raised, and the whole forming a con- 

 siderable projection ; another small avicularmm on a distinct elevation external to 

 this and on a lower level'. 



S.P. ; M.C. 



In this very peculiar form the thyrostome is Lepralian, but the peristome is 

 very much elevated and appears, owing to its deficiency below, like a short tube 

 with a slice cut out of the lower side, the upper part having a hood-like appearance. 

 The avicularia are arranged in a manner quite different from what is found else- 

 where. There are two on the external side of the thyrostome. One is close to it 

 and has its inner side incorporated with the peristome ; the other is separated and 

 situated externally, reaching close to the junction of the zoarial lamina. These 

 external avicularia are arranged almost in a special tract, separated from the 

 corresponding series of the other lamina by a slight ridge, those of the two series 

 being opposite to each other. 



Pachystomaria, n.g. 



Zoarium unilaminate. Zooecia broad above, narrowed below, oblique ; surface 

 cribriform ; thyrostome rounded or elliptical ; peristome much thickened, entire, 

 and, as well as the portion of the zooecium immediately below and to the sides, 

 elevated ; in the only species a large triangular avicularium to one side of the 

 thyrostome. 



1. JP. parvipuncta, n.sp. PI. VIII., fig. 24. 



Zocecia in obscurely radiating series, wide above, narrowed below ; surface, 

 except above, perforated by numerous small, close-set round pores, the margin 

 forming a slightly thickened rim ; upper part, immediately below and to the sides of 

 the thyrostome and avicularium, raised, and with a few large irregular rounded or 

 elongated pores ; thyrostome transversely elliptical, the peristome much thickened ; 

 a large broad avicularium, with triangular mandible directed upwards and outwards, 

 below and to one side of the thyrostome. 



M.C. 



Of this very interesting species I have only two incomplete but well-preserved 



specimens. They are both unilaminate, convex anteriorly and concave posteriorly. 



The zocecia are arranged in an irregularly radiating manner. In one specimen the 



dorsal surface is fomied by radiating series of convex ridges, with a few pores or pits 



contracted at intervals and separated by deep grooves, exactly similar to the 



structure found in many species of Selenaria and Lunulites. In the other the 



o 



