Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/90

60 poriform body, and then passes across the line of the posterior lateral ambulacra, turning forwards in the inter ambulacral space and being visible thence to about mid way bet ween the apical system and the ambitus in front (Pl. IV. fig. 8). The fasciole then crosses the ridges on either side of the odd ambulacrum and completes the circuit. The band of small granules constituting the fasciole is narrow, but very distinct; but the anterior transverse portion is not very marked. The cavity for the odd ambulacrum is moderately deep, and has on either side towards the apical system a ridge which is ornamented with numerous small tubercles encircled by miliaries. The abortion of the anterior poriferous zones of the antero-lateral ambulacra is evidently in relation to the presence of the internal fasciole. Our knowledge of the subanal spectacle-shaped fasciole (Pl. IV. fig. 6), first noticed by Laube, and subsequently by Mr. Etheridge, may be thus added to:—It commences in a mass of miliaries on the subanal plates, and then passes outwards and curves downwards. The union is made with that of the other side by a narrow transverse line of granules, which, as a fasciole, passes across the intervening space. The curved upper part of the fasciole on either side is, in some specimens, prolonged inwards so as to incompletely include a space which is ornamented with small tubercles, the scrobicules of which are separated by ridges. These tubercles have the mamelon very distinct; and in their neighbourhood are smaller ones in more or less definite rows, and some in a part of a circle bounding the fasciole internally.

The outer curve of this fasciole (on either side) is within the range of the posterior lateral ambulacrum, the plates of which, as they are continued to the ambitus, pass down beneath the ornamentation of the outer part of the fasciole and the outer part of the included space. It results that there are five or six pores in these plates which appear within the fasciole (Plate IV. fig. 6), in a semicircle just on its inner edge. They are distinct in worn specimens, and can usually be distinguished in others close to the tubercles. The periproct may be round, ovoid, or elongated transversely; and the subanal space may be high or low in the same variety of the species; but in all, the ornamentation of the subanal space is very distinct, and consists of miliaries and a few very small tubercles.

The peristome has the posterior lip edged with a ridge of plain ornament; and behind this are rows of small miliaries succeeded by larger ones whose numbers become less and less. The posterior lip is bent downwards; and the anterior and lateral parts of the peristome pass upwards into the funnel-shaped cavity, which is semilunar transversely.

The floscelle is tolerably well developed; and the pores are distinct and belong to all the ambulacra, the anterior odd ambulacrum being nearly destitute of them; but it presents two pores on either side and the relics of the sphæridial space. A very beautiful ornamentation is seen around the floscelle, in front especially; and it includes that of the larger first polygonal peristomial plate (interradial). This is slightly convex and has pretty miliaries on it. Distinct but small tubercles with flat scrobicules are in and around