159 
general absence, or if they occur, the forms are of the genuine favositoid 
type.i 
Occurrence. —In fossiliferous Silurian limestone ; Cowombat Creek, N.E. 
Gippsland (No. 2134). 
Order Cryptostomata. Fam. Rhabdomesontid^. 
Genus Acanthoclema, J. Hall. 
Acanthoclema flexuosa, sp. nov. (Plates XXIV., Pig. 20 ; XXXII., Figs. 38-40). 
Description.—~Zodi,rmm moderately slender and branching; branches 
cylindrical or slightly flattened; basal portion swollen. Diameter of branches, 
2 to 4 mm. Apertures circular to ovate, inclined to be ostiolate, arranged 
in a vertical series more or less quincuncially. Number of rows usually 
about ten. Interspaces between the apertures occupied by a depressed 
vertical ridge. Zooecia disposed at an acute angle to the axis, but opening 
at the surface nearly at right angles. The primitive part of the zooecia 
bend sharply down to the axis. Acanthopores numerous, producing a 
roughened surface, seen in well-preserved moulds. Length of zoarium 
reaching 5 cm. or more. 
Observations .—-This form is probably the same as that referred to by Prof. 
McCoy as allied to Trematopora ostiolata, J. Hall^ from the Silurian of Cooper’s 
and Deep Creeks, Thompson River, Gippsland. T. ostiolata, whilst bearing 
a general outward resemblance to the above form, belongs to the trepostomate 
group, whereas the Victorian species now described is a cryptostomate form. 
The systematic arrangement of the zooecia in the two genera mentioned 
differ greatly, as seen in cross section, the intermediate vesicular tissue and 
central canal of the zoarium of Trematopora being absent in Acanthoclema. 
No sufficiently well-preserved specimens which could be cut for micro¬ 
scopic examination were found in this series, but in the general determination 
of this form from casts and moulds the writer has been greatly helped by a 
collection of palaeozoic polyzoa lately deposited in the National Museum 
by Dr. R. S. Bassler, of Washington, U.S.A. 
Acanthoclema asperum, J. Hall sp.,^ differs from the above in its more 
slender branches and nearly circular zooecial apertures. 
Occurrence. —-Well-preserved casts and moulds in indurated dark-grey 
Silurian shales ; Gibbo River, N.E. Gippsland (Nos. 2677-80, 2682, 2684-7, 
2691, 2694). 
Class Brachiopoda. 
Fam. Discinid^. 
Genus Orbiculoidea, d’Orbigny. 
Orbiculoidea diminuens, sp. nov. (Plate XXXII., Figs. 41, 42). 
Description. —-Shell minute ; upper or ventral valve subcircular, depressed, 
with a slightly subcentral pedicle notch. Surface of valve having eleven or 
more concentric and rounded ridges with interspaces deeply excavated. 
Greatest width, 3 • 25 mm. 
Relationships. —The Victorian specimen is a well-preserved cast in hardened 
mudstone, and a wax squeeze shows the minutest details of the valve. It 
agrees with Sowerby’s species, 0. rugata'^ from the Wenlock and Upper Ludlow 
of England and Wales, in the circular outline, the depressed form and the low 
vertex with close concentric rugse. Taking into consideration the facts 
^ " The Genus Monticulipora and its Subgenera,” 1881, pp. 93, 94. 
* Geol. Surv. Viet., Prog. Rep., No. 5, 1878, p. 175. 
* Trematopora aspera. Hall, Nat. Hist. N. York, Pal. II., 1852, p. 154, pi. XLA., figs. lOa-c. Batos- 
tomella aspera. Hall sp., Nickles and Bassler, Bull. U.S. Geol. Surv., No. 173, 1900, p. 189. Acanthoclema 
asperum. HaU., sp. Bassler, ibid., No. 292, 1906, p. 58, pi. XXI. figs, 3-5; pi. XXIV., figs. 7-9 ; pi. XXV. 
figs. 17-20. 
* Orbicula rugata, Sowerby, 1839, in Murchison’s Silurian System, pi. V., fig. 11. Discina rugata. 
Sow, sp., McCoy, 1852, Brit. Pal. Foss., p. 190. Davidson, 1866, Pal. Soc. Mon., Brit. Foss. Brach., pt. 
VII. No. 1, p. 63, pi. V., figs. 9-18. 
