63 
divided by a groove ; the double as well as the single ridge being surmounted 
by a row of prominent tubercles almost in contact with each other. Only 
one example of the tilling up of the mouths has been observed, but it affords 
satisfactory evidence of a gradual expausion of the inner band, before alluded 
to, and a final meeting in the centre.” 
Tabulse are very sparsely developed, and are often not recognisable at 
all, but when present are undoubtedly complete. In PI. VII, Pig. 9, two are 
visible just previous to the deflection of the tubes towards the periphery. By 
Prof. Nicholson and the Writer, the imperfect diaphragm of the vestil)ulc 
was spoken of as a perforate tabula,^ but lacking evidence as to the existence 
of true perforated tabulae as they exist in Stenopora fTahuliporaJ Howsei, 
Nich., it will be better, in the meantime, to refer to this structure as a 
perforated diaphragm only, without intending to convey by this term the 
homologue of a true tabula.. 
In our New South Wales rocks it seems to be particularly difficult to 
obtain specimens exhibiting the surface. This arises, possibly, from the 
tenaeious manner in whieh the numerous f)riekle-like aeanthopores adhere to 
the matrix. On the other hand, in Tasmanian examples the surface charaeters 
are usually well displayed, for the deposits in that island, characterised l)y 
Slenopora, appear to be more calcareous than do our Marine beds, and better 
adapted for the weathering-out of fossils. In S. tasmaniensis the acantho- 
pores are very numerous, often forming a complete ring round the mouth of 
the calice,^ as many as twelve having been counted in this position, on the 
somewhat angular interstitial surfaces. Or the aeanthopores may be placed in 
more or less longitudinal oblique rows, similar to the caliees, when the circular 
arrangement becomes gradually lost. When such is the case a depressed 
surfaee exists on the interstitial surfaee of the corallum, between contiguous 
rows of caliees, giving rise to the appearance of a groove, as shown in 
another of Lonsdale’s figures.^ 
The distinguishing points relied on for specific determination in S. 
tasmaniensis are ; — 1. The irregularity in the diameter of the branches, and 
its lesser size when compared with that of S. ovata. This is, perhaps, not a 
very stable character, as some speeimens of S. tasmaniensis attain a fair 
development, but I think it may be aecepted that, as a rule, it is smaller 
> See Ann. Mag. Nat. Hist., 1886, XVII, t. 3, f. V2. 
^ Strzelecki’s Phys. Descrip. N. S. Wales, &c., 1845, t. 8, f. 2 a-c. . 
Strzelecki’s Phys. Descrip. N. S. Wales, &c., 1845, t. S, f. 2d. 
lla 50—91 K 
