William Whitehead Watts was born at Broseley in Shropshire in 1860, and passed the critical part of his school life at Denstone. Here he came under the influence of the Rev. D. Edwardes, who taught him physics and chemistry, infected him with a love of science, and stimulated him to try for a scholarship at Cambridge. In spite of the winning of an exhibition, afterwards converted into a scholarship at Sidney Sussex College, supplemented by an exhibition from his old school, his maintenance at Cambridge was only accomplished by much self-sacrifice on the part of his parents.

In 1897 C. E. Beecher published his “Outline of a Natural Classification of the Trilobites”, which has since “proved superior to any previously proposed”. If early a score of years have passed since that time and many new Trilobites have been discovered, the majority of which fit into this system without difficulty and prove that to a large extent it is conceived on a sound basis. A few, however, do not fit in and have therefore revealed in it weaknesses, the existence of which tend to hinder the systematic study of Trilobites. In the following pages it is proposed to point out these weaknesses and to make suggestions for modifying and extending Beecher's system upon what it is hoped will prove to be natural lines.

In 1890 Vine described Membranipora gaultina a uniserial Cheilostome from the Cambridge Gault. A peculiarity of this species was ‘a puckering’ or ‘folding-in of the wall below the area’ shown by Vine in his figure of the type-specimen. Unfortunately this specimen cannot be found; but a well-preserved paratype specimen (from the same horizon and locality) exhibits the same structure and shows that this is due to the collapse of the extra-terminal front wall along a median line proximal to the aperture. Other zoœcia of the same specimen show the extra-terminal front wall entire and a thin median seam—or rhamma—running proximally from the aperture. The rhamma appears in some instances as a ridge and in others as a depression; in some zoœcia it is not apparent; and when visible is extremely fine. In many cases the front wall is broken along it (as in Vine's figure) and thus the rhamma probably indicates a line of weakness. It is suggested that the rhamma is a ridge bounded by two furrows and that the front wall is thicker at the ridge and thinner in the furrows. The rhamma, then, would easily be broken off, and in such specimens a depression would appear in its place; and a thin groove on each side would constitute a general line of weakness which would account for the frequent breaking down of the front wall.

In the preceding paragraphs it has been shown that, after the inland ice had attained its southernmost limit and had spent its force, there commenced in Southern England the last of many stages of land depression. This carried with it a complete reversal: the temperature was raised, the periphery of the inland ice melted, its pressure was lessened, and a rapid rise of the land—the Mousterian elevation—introduced a great rise, to which the origin of the submerged forests bears witness. Nevertheless, the greatest part of the land depression persisted even after Mousterian time, and this explains the continuance of the melting and its increased rapidity, as well as the rapid northward withdrawal of the inland ice, which we shall soon consider.

Another type, which is found in both quarries and which under the microscope has the aspect of a monchiquite or limburgite,. probably represents the actual marginal rock of the intrusion. It consists of small microphenocrysts of augite and olivine in a dark matrix, which can be resolved into granular augite and magnetite in a nearly isotropic base. The latter, which sometimes contains felspar microlites, seems to be mainly analcite with some nephelite, as it can be readily gelatinized and stained, while the refractive index is very low. The felspar microlites are small and sometimes have a rough trachytic structure resembling that of the mugearites. Following Harker's suggestion that augite-olivine rocks with an isotropic base should be classed as limburgites when the base is glass and as monchiquites when it is analcite, this rock can be included in the latter, group. The parts which are richer in felspar may be termed analcite-basalts.