Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/85

Rh anterior and in the antero-lateral interambulacra there are large primary and secondary tubercles irregularly arranged and sparsely distributed, but occupying the whole of the spaces. The primaries have a perforated mamelon, crenulated boss, and a flat scrobicule. The edge of the ambitus is rather sharply rounded. The actinal surface slopes upwards in front anterior to the mouth, and is more or less convex posteriorly, on account of the sharp keel of the posterior extremity of the interambulacral actinal plastron. The mouth is slightly sunken anteriorly; and the posterior lip is rounded and projects downwards slightly, being, unlike the rest of the circumference of the opening, very tuberculate (Pl. III. fig. 16). The actinal anterior and lateral ambulacra form short and almost smooth avenues; and the posterior ambulacra form wide, almost smooth bands extending from the subanal fasciole on either side of the keel to the sides of the mouth and behind the posterior lip. The anal system is large, and almost circular in outline, and is situated in the obliquely truncated posterior extremity, of which it occupies nearly one half (Pl. III. fig. 17). The subanal fasciole is closed, heart-shaped, and reaches to the point of the keel of the plastron. The poriferous areas of the anterior odd and paired ambulacra on the actinal surface show a few slit-like pores surrounded by a scrobicule-like rim, which occupy the position of large tubercles. There are also corresponding pores in the posterior ambulacral zones close to the mouth. The tuberculation of the anterior interambulacra on the actinal surface is larger near the mouth, and so is that of the lateral interambulacra; but the tubercles diminish in size and increase in number towards certain points on the ambitus; within the posterior actinal interambulacral space the tubercles radiate from the point of the keel, and the largest are the remotest from it. The mouth is large, broader than long, curved in front, and encroached upon behind by the projecting posterior lip.

Length 2 inches, breadth 2, height of vertex 1 inch.

Locality.—Tertiaries of the Murray river.

, sp. nov. Plate III. fig. 18.

The test is thin, depressed, elliptical in outline, but narrow and somewhat pointed posteriorly. There is slight truncation of the posterior interambulacrum. The antero-lateral and posterior petals are nearly equal in length and breadth, and are lanceolate, the anterior pair diverging more than the others. The poriferous zones of both ambulacra are equal in breadth, are slightly sunken; and the anterior poriferous zone of the antero-lateral petals is the smallest. The pores are conjugate, those of the antero-lateral zones being the largest; and in both ambulacra those of the inner row are rounder and smaller than those of the outer, there being 13 or 14 rows in each petal. The interporiferous zone is slightly convex, and has miliaries and third-sized tubercles; and miliaries crowd the elevations between the successive pairs of pores. The anterior odd ambulacrum is nearly flush, bounded by tubercles larger than those within its area, and contains a few pores. The apical system is