The spines are very delicate and hollow, with projecting processes arranged in an imperfect spiral; and resemble somewhat the small spines of the Diadematidæ. The colour of the test is a rich crimson with a dash of purple, and it is very permanent; the only perfect specimen procured which is

preserved in spirit has not lost colour greatly to the present time.

In the summer of 1870, Mr. Gwyn Jeffreys, dredging on the coast of Portugal, took two nearly perfect specimens and several fragments of another species of the genus Calveria; and subsequent careful examination of fragments and débris has shown that this second species, C. fenestrata, occurs likewise in the deep water off the coast of Scotland and Ireland. The interambulacral plates are plates are narrower, and leave larger membranous spaces between them, and the great key-like overlapping expansions in the middle line are much larger. The spines have the same form and are arranged nearly in the same way; hut parallel to the outer row of large spines

FIG. 29.-Calveria fenestrata, WYVILLE THOMSON. One of the four-valved pedicellariæ.

on each interambulacral space there is a row of four or five or more pedicellariæ, of quite a peculiar type. The head of the pedicellaria which is supported on a long stalk, consists of four valves (Fig. 29), the wide terminal portion of each forming

a beautiful double fenestrated frame, with a peculiar twist in it reminding one of a Campylodiscus, and a very elegant crenated border. These disks are raised on delicate hollow pedicels, which expand beneath, at their point of attachment to the common stalk. A large mass of muscle envelopes the lower part of the group of pedicels, and doubtless determines the movement of the valves in reference to one another.

It is difficult to see what relation in position the valves can occupy when the instrument, whatever may be its use, is closed.

We now steamed onwards to the south-east for about ten miles, and put down our dredge, fully equipped with hempen tangles' and every accessory device for entrapping the denizens of the deep, exactly, as our Commander assured us, over the spot where we had dredged the Holtenia early in the cruise. We got there in the evening, and adopted a plan which we had tried successfully once or twice before; we allowed the dredge to remain down all night, moving along with the drift of the vessel, and hauled it up in the early morning. I do not believe human dredger ever got such a haul. The special inhabitants of that particular region-vitreous sponges and echinoderms-had taken quite kindly to the tangles, warping themselves into them and sticking through them and over them, till the mass was such that we could scarcely get it on board. Dozens of great Holteniæ, like

“Wrinkled heads and aged, With silver beard and hair,"

a dozen of the best of them breaking off just at that critical point where everything doubles its

weight by being lifted out of the water, and sinking slowly away back again to our inexpressible anguish; glossy whisps of Hyalonema spicules; a bushel of the pretty little mushroom-like Tisiphonia; a fiery constellation of the scarlet Astropecten tenuispinus; while a whole tangle was ensanguined by the disjecta membra' of a splendid Brisinga.

There was not much in the dredge-bag that was new. Some large Munide, with their sphëery eyne;' some fine specimens of Kophobelemnon mülleri; an example of the Euryalid, Asteronyx lcvéni, nearly the only Scandinavian echinoderm which we had not previously taken; and an injured specimen of a flexible urchin, which we supposed to be of the same species as that procured the day before, although it differed greatly in colour, being of a uniform pale grey. Upon further examination, however, it proved to be the type of a totally different generic group of the same family.

Phormosoma placenta resembles Calveria in having the perisom flexible, the plates overlapping in the same way and in the same directions; but the plates overlap one another only slightly, and they leave no membranous spaces between, so that they form a continuous shell. The great peculiarity of this form is that the upper surface is quite different from the lower. Above, the ambulacral and interambulacral areæ are well defined and in ordinary proportion, the interambulacral areæ being just twice as wide as the ambulacral, and the spines are much like those of Calveria, and are arranged nearly in the same manner. At the periphery the shell comes to a kind of ridge, and alters entirely; from the edge

M

to the mouth the distinction between ambulacral and interambulacral area is apparently lost, and the sutures between the plates can scarcely be made out; the pore areæ are reduced to mere lines of double pores, and the whole of the surface of the shell is studded over uniformly with the very large areolæ of primary tubercles, bearing spines which are small and delicate and apparently quite out of proportion to the mass of muscle connected with them which fills the areolæ. As in Calveria, the tubercles are perforated.

We have thus become acquainted with three members of a family of urchins which, while differing in a most marked way from all other known living groups, bear a certain relation to some of these, and easily fall into their place in urchin classification. They are 'regular echinids,' and have the normal number and arrangement of the principal parts. They resemble the Cidaridæ in the continuation of the lines of ambulacral pores over the scaly membrane of the peristome to the mouth, and they approach the Diadematidæ in their hollow spines, in the form of their small pedicellariæ, and in the general structure of the jaw pyramid. From both of these families they differ in the imbricated arrangement of the plates and in the structure of the pore area, to the widest extent compatible with belonging to the same sub-order.

Many years ago Mr. Wickham Flower of Park Hill, Croydon, procured a very curious fossil from the upper chalk of Higham near Rochester. It consisted of a number of series of imbricated plates radiating from a centre, and while certain sets of these plates were perforated with the characteristic double

pores of the urchins, these were absent in alternate series. Some points about this fossil, particularly the imbricated arrangement of the plates over portions indicating a circle at least four inches in diameter, caused great difficulty in referring it to its place. Edward Forbes examined it, but would not hazard an opinion. The general impression was that it must be the scaly peristome of some large urchin, possibly of a large Cyphosoma, a genus abundant in the same bed. Some years after the discovery of the first specimen, a second was obtained by the Rev. Norman Glass, from Charlton in Kent. This specimen appeared at first to solve the difficulty, for it contained in the centre a well-developed lantern of Aristotle;' there then was the peristome of the urchin, of which Mr. Flower's specimen was the periproct. The late Dr. S. P. Woodward examined the two specimens carefully, and found that the question was not so easily settled. He detected the curious reversal of the imbrication of the plates in the ambulacral and interambulacral area which I have described in Calveria, and at one point he traced the plates over the edge of the specimen, and found that they were repeated inverted on the other side. With great patience and great sagacity he worked the thing out, and came to the conclusion that he was dealing with the representative of a lost family of regular echinids.

Woodward names his new genus Echinothuria, and describes the chalk species, E. floris, almost as fully and accurately as we could describe it now with a full knowledge of its relations -- for Echinothuria is closely related to Calveria and Phormosoma. In all