Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/82

52 generative pores. The anterior ambulacrum is in a shallow groove, and its small pores, rather crowded above, become more distant and larger towards the ambitus; they are oblique in direction, round, and nearly equal, in pairs, being separated by a very delicate septum.

The pores of the antero-lateral ambulacra are small, equal, round, and wider apart and larger towards the ambitus, where the zones are wide apart. The posterior pair of ambulacra are rather close together, and the pores resemble those of the others. The periproct is small and situated in the truncated posterior part. The actinosome is at the anterior third; it is sunken, transverse, and the posterior lip passes into a prominent keel-like plastron. The ornamentation is very simple: there are no large or even secondary tubercles; but small tertiaries and miliaries exist, generally scattered.

Length 1 inch, greatest breadth a line or two less; height in front and behind  inch.

Locality.—No. 5, Upper Coralline Beds, Castle Cove, Cape Otway.

, sp. nov. Plate IV. figs. 1–4.}}

The test is thin, depressed, and the outline from above is irregularly oval and rounded anteriorly. There is a slight indentation at the ambitus, made by the shallow anterior groove; and the shape is rather angular posteriorly in the anal region, and broadest midway. The sides of the test are sharply rounded, slightly angular. The abactinal surface is highest posteriorly on account of the anal keel, which, being produced backwards, is also sloped and depressed anteriorly between the posterior petals. The apical system is small, and the four large genital openings are close to each other (Pl. IV. fig. 1), the madreporiform body passing backwards; it is in advance of the centre and anterior to the depression already noticed. The anterior and shortest petaloid ambulacra are lanceolate, and are almost transverse. The poriferous zones slope up to raised, broad interporiferous zones; and the external rows of pores are the largest, and usually more oval than round. The posterior rows are better-developed than the anterior, which are imperfect near the apical system. About 21 rows of pores exist, all of which are conjugate.

The posterior ambulacra are long, broad, flush, and wider posteriorly than anteriorly; they are nearly parallel with each other, and bound the keel on either side. The external poriferous zones are curved; the internal are much less so; and the interporiferous zones are much broader than those of the antero-lateral petals, and there are traces of two or three large secondary tubercles within their area. The odd anterior ambulacrum is nearly flush with the test, except at the ambitus, where there is a slight depression; its pores are numerous near the apical system, and are very small; elsewhere they are very rare. This ambulacrum is bounded externally by plates rather raised above the general level; they are tuberculate with large crenulate and perforate miliaries, and they separate it from the plates with the large tubercles of the anterior interambulacra. The anterior interambulacra have several horizontal rows of large and of secondary tubercles mixed and increasing in