(1) The Carbonicola fallax group of shells, which characterize the Lenisulcata Zone of the Coal Measures, is an extremely variable one comprising a wide range of forms, between which there appears to be perfect gradation.

(2) The hinge of the group is also a highly variable feature, bearing little relation to the outline of the shells. Its variation, however, is more fully known in small forms than in large ones.

(3) Evidence submitted in the present paper indicates that, although the hinge pattern of the C. aquilina group may not be as constant a feature as has hitherto been supposed, the group is distinct from that of C. fallax. There is no evidence suggesting genetic relationship. A basis for the distinction between internal moulds of C. aquilina and C. fallax is fully described.

(4) The basic features of the hinge of the C. fallax group are essentially those which characterize the Carbonicola pseudorobusta–C. communis group of the Ovalis Zone. While certain of the hinges of the larger shells appear typical of the latter group there are a number of other patterns which have not previously been described in the Carbonicolidae.

(5) The hinge features of the C. fallax group appear less specialized than those of shells from the Ovalis Zone, especially Carbonicola pseudorobusta Trueman (MacLennan, 1944).

(a) Large strong teeth have not been seen. Definite small teeth are not commonly developed. It is usual to find gentle swellings on the hinge plate corresponding to depressions in the opposing valve. Some forms are quite edentulous.

(b) Only one tooth has been found in either valve, although more than one swelling or depression may be present. There is no approach to the more complicated patterns figured by MacLennan (1944).

(c) In most cases engagement of the dental apparatus would only take place as the valves opened. Notches or sockets in the hinge plate are not necessarily opposed by teeth or swellings, but they would have been more or less filled as the opening continued, when the hinge plates apparently rolled against one another.

(d) In a community of small shells there is evidence to suggest that in several cases the hinge margin of the left valve slightly overlapped that of the right for a short distance anterior to the umbo.

(6) The range of variation of hinge characters in a community is very large. Collections from different horizons, however, may indicate individual peculiarities or tendencies in the variation. Whether these owe their origin to local conditions or evolution is not yet clear.

(7) The hinge of Anthracomya from the Lenisulcata Zone is as yet little known. What evidence there is points to a hinge similar to that of small Carbonicola showing the same type of variation.

The grits and conglomerates in the Etruria Marls of North Staffordshire include types with a chamosite-rhombohedral carbonate cement containing interesting spherulitic and concentric structures. Manganese appears in this cement and in certain calcareous bands in the argillaceous fades of the Marls. The clastic fragments suggest derivation from Pre-Cambrian and Cambrian rocks. The heavy mineral suite resembles that listed by Fleet for similar horizons in the Midlands, but staurolite is recorded also.

There is no new evidence bearing on Robertson’s hypothesis that basic igneous rocks of Carboniferous age have contributed to the formation of the Etruria Marls.

The new genus here proposed is based on nine specimens. All are more or less complete crowns. The best preserved example (Plate III, figs. 1, 2, 3, 5) was previously illustrated in Trans. Roy. Soc. Edin. as Synerocrinus incurvus (Trautschold) (Wright, 1939–1940, pl. xi, fig. 8). Later, the discovery of another well-preserved specimen caused some doubt about this interpretation and led to further cleaning and developing not only of the first mentioned specimen, but of others in my collection. Some of these were labelled as Synerocrinus incurvus (Trautschold) or the kindred species Amphicrinus scoticus Springer. From a study of all these specimens it is now evident that we are here dealing with a crinoid which differs in certain aspects from Synerocrinus or in fact from any other described Ichthyocrinid. Two specimens previously figured as Amphicrinus scoticus Springer (Wright, 1914, pl. xix, fig. 4, 1939–1940, pl. xi, fig. 2) are now here referred to the new genus.

The most representative series of fossiliferous pebbles from the Birmingham district is that in the Evans Collection, which was acquired by the National Museum of Wales in 1937 and catalogued under the numbers 37.110 GR 1–316. For the loan of this collection I am indebted to Dr. F. J. North, and material for comparison from other collections was obtained from Dr. C. J. Stubblefield, Miss J. R. Harding, and Professor L. J. Wills, who has also corrected the typescript.