Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/77

Rh by some authors Echinanthus testudinarius, and by others Clypeaster testudinarius, that there can be no hesitation in identifying this fossil with that species. Except in some slight points in which there is great individual variation in the recent forms, the fossil agrees with those which Gray called Echinanthus testudinarius and E. australiæ, the latter of which has been absorbed by the former.

The species is interesting from its close resemblance to a Clypeaster; but it has no pores close to the sutures of the plates within the ambulacra on the actinal surface.

Locality.—Lindenow, Mitchell River, Eastern Victoria.

, sp. nov. Plate III. figs. 6 & 7.

The test is roundish, subpentagonal, flat, rising slightly towards the apical disk, and slightly concave on the actinal surface. It has the same longitudinal and transverse diameter. The apical disk is slightly in front of the centre.

The ambitus is sharp, and is incised at the end of each ambu- lacral groove ; and there is a rounded excision at the periproct, which is just under the margin. The ambulacra are grooved longitudinally, and swell up on either side ; and they occupy about an equal space with the interambulacra, where they are comparable. The poriferous zones reach about halfway to the ambitus, and are broad and turn in slightly. The ornamentation in the ambulacral spaces is oblique and banded, but it is without any order on the interambulacra.

On the actinal surface this oblique ornamentation is seen on either side of the ambulacral groove ; and this groove enlarges near the peristome, which is subcircular. Traces of sphasridia on one side of the groove are observed.

Length of large specimen 2 inch; breadth 2 inch.

Locality.—Mordialloc, Section 2. No. 1 and No. 3, and from soft yellowish white limestone at the mouth of Curdies River, about 30 miles east of Warumbool, which is in the upper part of a series underlain unconformably by Miocene calcareous clays.

This species, eminently Arachnoidean, has, however, more defined excisions on the ambulacra at the ambitus than either of the living forms, A. placenta, Linn., and A. zelandiæ, Gray—the one from the whole eastern coast of Australia, and the other from New Zealand. The situation of the periproct is variable in the genus Arachnoides, and is not invariably supramarginal. It may be marginal and slightly sub- or inframarginal; and this last appears to be characteristic of the fossil forms. The resemblance between the ornamentation, the sphaeridia, the actinal grooves, and the petals of the ancient and modern forms is very remarkable.