antero-ventral margins which form a broadly convex outline. Their truncated posterior borders are slightly sinuous-being projected backwardly just below the articular socket, and having a slightly excavated outline below this. The posterior borders bear minute marginal denticles, and they form a roughly rectangular junction, below, with the antero-ventral border. There is a shallow vertical groove on the surface near the posterior border, and the pleuron also bears granular and pitted ornaments on its upper and posterior parts. Posteriorly situated, on its lower half, are two short, parallel, raised ridges bearing several minute tubercles: these have a transverse (horizontal) direction, and the lower is the shorter of the two. On the pleura of the succeeding three segments (iii.-v.) the ornaments are similar, but the horizontal tubercular ridges become reduced in size, particularly in the fifth segment. The pleura of these segments are much less extensive than those of the second segment. Those of the third and fourth segments are pointed below, with sloping, slightly convex, antero-ventral borders, with narrow smooth raised marginal lip and straight posterior borders furnished with a row of minute denticles. The pleura of the fifth segment are more broadly rounded below. Those of the sixth segment are very reduced in extent and have the posterior half of their inferior margin broadly excavated to allow of the free movement of the expanded swimming appendages of this segment. The pleura and tergum of this segment are alike ornamented with minute tubercles.

The tergum of the first abdominal segment has a shallow groove rising from the articular sockets and curving slightly forwards as it crosses the back. Similar grooves occur on the succeeding four segments, two on either side of each tergum. They arise at the (anterior) articular facet and the (posterior) articular socket and slightly converge as they pass up towards the dorsal arch of the tergum. The anterior groove on the second segment may be traced across the back, but the remaining grooves become very faintly marked or disappear on the dorsal parts. On the sixth segment, the corresponding anterior groove is very strongly marked, and passing right across the back, defines an anterior, convex, lenticular shaped tergal facet which fits under the posterior part of the fifth tergum. There is also on either side, in the posterior half of the segment, a horizontal groove, separating the pleuron from the tergum, and these pass posteriorly into a very weak shallow groove which runs across the tergal arch close to the posterior border of the segment.

The telson is relatively narrow and elongated. Its sides form

approximately straight outlines in the anterior half and converge very gradually at first, but more rapidly in the vicinity of the narrowed, rounded, posterior margin. The anterior margin is almost straightly transverse, and forms roughly rectangular junctions with the sides. The dorsal surface of the telson is of flattened form, curving down abruptly at the lateral margins. There is a weak median longitudinal ridge which dwindles away posteriorly before reaching the hinder border. At a distance of about one-quarter of the total length of the telson from its anterior border there arises from the median ridge on either side a curved, narrow ridge, bearing granules or minute tubercles. These first pass backwards, and, diverging from the median ridge, they curve outwards and pass obliquely forwards to the antero-lateral angles of the telson. Each encloses a roughly ovate area of the dorsal surface which is almost smooth, or has very sparse granular ornaments. The remainder of the surface of the telson has evenly spaced granules or minutely tubercular ornamentation.

The appendages of the abdominal segments are unknown, except portions of the expanded swimming organs of the sixth segment; but these are too imperfectly preserved for precise description.

Dimensions.—The largest specimen examined measures 38 mm. along the median dorsal line from the tip of the rostrum to the posterior end of the carapace. The greatest height of the carapace in this specimen, if it were perfect, would be about 16 mm. Other individuals, in which the rostral region is absent, have a similar heightmeasurement, and the total breadth of their carapaces measured in cross-section does not appear to exceed 8 mm., although the specimens have not suffered appreciably from lateral crushing. The length of the abdomen in extension cannot be accurately measured owing to the flexion assumed at death, but it may be estimated to have been approximately the same as that of the carapace.

Occurrence. Several specimens were obtained by Mr. Rogers from a bare slope W. 30 S. from the middle of Barkly Bridge, on the farm Olifant's Kop (35h, 37h, 38h).

A specimen consisting of portions of a thoracic limb which may belong to this species is from the collection of the South African Museum and is labelled "Sunday River" (663, on white label).

Remarks. Since the term "epimeron" has been used in two distinct senses by different authors, the term "pleuron" has been retained in the above description to denote the downward lateral prolongation of the tergum of each abdominal segment on either.

side. The usual condition of the abdomen is one of flexion, with the pleura overlapping one another in a marked degree; but one of the specimens examined (38h) shows segments iii.-vi. so extended that the form of the pleura is well exhibited. It will be noted that the conventional terminology here used in reference to the main divisions of the body is that which is most widely known and employed.

The transverse grooves on the terga of the abdominal segments mark the degree of overlap of the segments when these are in the position of extension. The grooves probably correspond with strengthening ridges on the interior surface of the terga which pass upwards from the ball (anterior) and socket (posterior), respectively, of the lateral articulations in each segment. The depth and the dorsal continuity of the anterior groove in the sixth segment, and the smooth, convex, well-developed rolling facet anteriorly to it, which fits closely under the hinder part of the fifth tergum, appear to be contrivances for securing the rigidity and strength called for in the exercise of rapid and vigorous movements of the tail in swimming or springing. The tergal facets of the preceding segments are much less well developed and defined.

Meyeria schwarzi differs widely from M. ornata (Phill.),* from the Speeton Clay, in the absence of the characteristic ornaments on the abdominal terga and in the form of the pleura, as well as in other features. From M. magna M'Coy [= M. vectensis Bell], of the Aptian of the Isle of Wight, it is readily separable by the absence of ornamenting granular ridges on the abdominal terga, by the weaker development and different position of the oblique branchial fold or carina, and by the form of the pleura. M. magna also appears to be a much larger and more robustly formed species. It may be remarked that the fragment of an elongated ambulatory leg (South African Museum collection, No. 663), mentioned above, bears much resemblance, in its relative proportions and in its tuberculated ornamenting keels, to the long and slender anterior thoracic legs of M. magna.+

There appears to be very considerable resemblance between M. schwarzi and M. rapax Harbort, § from the Lower Valanginian of North Germany. Both have a smooth surface in the abdominal terga i.-v., and the form and ornamentation of the pleura are very

* Bell (1), p. 33, pl. ix., figs. 9-11.

† M'Coy (1), p. 334; Bell (1), p. 33, pl. x.

Bell (1), pl. x., figs. 1, 4.

§ Harbort (1), p. 11, Taf. i., fig. 12; ii., figs. 1-4; iii., figs. 1, 2; xi., figs. 1, 2.

similar. M. rapax, however, attained much larger dimensions and more robust form than any of the specimens of M. schwarzi examined, and it appears also from Dr. Harbort's figures that the cephalothorax of his species has less relative lateral compression. Other differences that may be noticed are as follows. In M. rapax the development of the obliquely running blunt branchial keel is much more pronounced; the anterior margins of the abdominal pleura are denticulated; the sixth abdominal segment has greater lateral depth and is not so depressed dorsally as the corresponding segment in M. schwarzi. Further, Dr. Harbort makes no mention of distinctive ornaments on the telson such as those which characterise the African form. The little smooth oval area at the anterior end of the branchial groove, which is well marked in M. schwarzi, does not appear to be an evident feature in M. rapax, if developed at all, and the same may be said of the grooves of attenuated sigmoidal form in front of the cardiac region of the carapace.

With reference to the above-mentioned small, smooth, oval area, which is situated on either side of the carapace on the anterior part of the branchiostegite, this structure is well represented also in Meyeria magna M'Coy, but does not seem to have attracted special attention. Its significance is not obvious, but it appears to be homologous with the similar areas on the carapace of Pseudoglyphæa. These were considered by Oppel to be a constant characteristic of that genus, and he referred to them as "reniform eminences," but did not enter into the question of their meaning. Corresponding structures of modified form may also be seen in some species of Glyphæa.

*

(A). LISTS OF THE FOSSILS CRITICALLY EXAMINED. The lists of fossils collected by Messrs. Rogers and Schwarz in 1900 and by Mr. Rogers in 1905 should be read in connection with the published official reports by these authors, which contain the records of additional forms seen by the Surveyors to occur at some of the localities. Thus, for instance, in the first report, among the fossils stated to have been found in the Marine Beds at Grass Ridge, near Uitenhage, there are the names of ten Mollusca, specimens of which were not brought away. In the later report by Mr. Rogers, many fossils are in like manner recorded, which are not represented in the collections submitted for examination. 1

(1) ZWARTKOP'S RIVER.

(Specimens collected by Messrs. Rogers and Schwarz, 1900.)

a. Railway cutting between milestones 241 243 on the railway from Uitenhage to Graaff-Reinet, about 3 miles from Uitenhage.

b. Grass Ridge, 3 miles east-north-east of Uitenhage.

c. Krantz near Picnic Bush, north-east of Red House.

Astarte (Eriphyla) herzogi (Goldf.)

(328)

d. Kloof on the left side of Zwartkop's River, east-north-east of