. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 282 Mr. Toulmin Smith on the Classification that a section of the entire body presents an a ,g" 'a outline as in fig. F, in which a—b is the sec- tion of the head. The outline of the head is always quite as sharp and well-defined as in this figure. The relative arrangement and proportions of the head and the plaits are such that specimens of this division can never be confounded with any belonging to the section Dilatati. It is very rarely in the present division that the
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 282 Mr. Toulmin Smith on the Classification that a section of the entire body presents an a ,g" 'a outline as in fig. F, in which a—b is the sec- tion of the head. The outline of the head is always quite as sharp and well-defined as in this figure. The relative arrangement and proportions of the head and the plaits are such that specimens of this division can never be confounded with any belonging to the section Dilatati. It is very rarely in the present division that there is any rounding, or departure from the nearly flat character of the head; a character, on the other hand, never present in the Dilatati. It is proper to notice that, in every species of this genus, in order to give full strength to the head, the depressions, bulgings, and other modifications of the fold,—where it does not rise, as in C. campanulatus, in a simple form,—are so arranged that the membrane of the inner wall, where it adjoins the head, is always, and that of the outer wall most frequently, expanded by a lateral bulging of the plait, so as for the adjoining plaits to meet just at the point of union of the wall with the head. Thus the whole of the inner, and often of the outer, edge of the head is continuously attached to the wall, an arrangement of much im- portance. On this inner edge the membrane often rises up in a narrow and slightly prominent ridge above the otherwise smooth surface of the head. 2. Cephalites guttatus. PI. XIV. fig. 2. Plaits broad and deep : outer plaits raised in large hollow bosses, often elongated ; adjoining plaits having an occasional lateral connection : inner plaits depressed at regular intervals, bulging on each side around depressions till adjoining plaits meet and open into each other : processes very conspicuous : wall usu- ally thick. Nothing can better express the usual character of this species than the term guttatus. The
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