204? 
coarsly wrinkled and striate, slightly imbricately laminate, crenu- 
lating the lateral angles. Exotheeal outgrowths not observed. 
Obs . — The principal characters of R. interpunctatum are its 
remarkable Calceola-like outline, prominent counter septum, and 
highly and coarsely vesicular structure. The relation in which 
R. interpunctatum stands with regard to R. australe has already 
been commented on, but the form, and more highly developed 
septa will tend to separate the species. 
In outline R. interpunctatum approaches nearest to Rhizo- 
phyllum gotlandicum , F. Roemer, * and R. tennesseense^ I . 
Roemer, t* but it is a smaller species, and the longitudinal curve 
of the corallum is proportionately greater in relation to its size. 
The septa in R. interpunctatum , unlike those of G oniophyllum 
pyramidale , are completely hidden by the highly developed 
vesicular tissue, instead of passing over the latter and disappear- 
ing at the bottom of the calice. Mr. Mitchell’s specimens are in 
the form of internal casts of the calice, with the vesicular tissue 
removed, precisely in the same condition as Re Koninck s were. 
The septa on the ventral side are vertical and increase in length 
from the lateral angles towards the counter septum. They are 
very finely granulated, and when in the least degree worn, with 
their angular inner sides rubbed off, appear double. No doubt 
Lindstrom’s suggestion that each is composed of two laming 
satisfactorily accounts for this. In counting the septa this 
feature must be taken careful note of, otherwise the total numbei 
will be accepted as exactly double. At the lateral angles and on 
the dorsal side of the calice the septa are represented by minutely 
granulated, very fine ridges, the granules in a single row, conform- 
ing in the curvature to the outline of the corallum. 
Locality and Horizon . — Hattons Corner, near Yass (J. A. 
Wall), Silverdale ( J. Mitchell); Upper Silurian, probably Wenlock. 
Collections .■ — Australian Museum, J. A. Wall, and J. Mitchell. 
General Remarks . — Both Rhizophyllum australe and R. inlet - 
punctatum agree with the genus Rhizophyllum , rather than 
Calceola, in the highly and openly vesicular nature of the corallum. 
On the other hand, the total apparent absence of exotheeal 
structures in the form of anchoring stolons from the flattened 
under surface show a departure towards the last named genus, in 
which there is no trace of them. The arrangement of the vesi- 
cular tissue of the corallum is precisely similar in both our species 
to that seen in Goniophyllum — infundibuliform layers, with the 
convexities of the vesicles directed upwards and inwards. This 
structure is particularly well shown in one of Mr. Wall s speci- 
mens of R. interpunctatum (PL xxx., Fig. 7), from which t le 
epitheca has been removed by weathering. It is also apparen t 
# Lindstrdm, Bihang K. Vet. Akad. Handl. Stockholm, 1882, vii. No. 
3 f Sil. Fauna Westl. Tennessee, 1860, p. 77, t. 5, f. 1. 
