Plate 13, fig. 2; plate 14, figs. 3–5.

Description of Genotype and Holotype.—An imperfect fish, consisting of three portions.

1. A slab, 24 × 12 cm., showing 6 vertebral bones, rays of the dorsal fin, ventral fin, and squamation of the median part of the body.

2. A crushed slab, 14 × 9 cm., showing crushed facial bones (? quadrate and pterygoid), part of mandible with teeth, and on the opposite face of slab, the preopercular.

3. Fish remains, 13 × 5 cm. on slab of mudstone, with a complete left pectoral fin.

Vertebrae.—The series of abdominal vertebrae shown here are of much the same contour as those in the recent Barracouta (Thyrsites atun), but on the whole much stouter and heavier. One of these centra has a length of 27 mm. and a maximum diameter of 19 mm.; in the middle of the centrum it narrows down to 12 mm. The rounded border of the adjacent centra indicates the former existence of a distinct cartilage pad, as in Thyrsites.

Pectoral Fin.—Narrow, slender, and only slightly curved; the proximal end shows a distinct articulating surface for attachment to the brachial. The rays are bony, narrow, and closely fasciculated. The length of the fin is 70 mm., and the greatest width 21 mm.

Teeth.—These number 5 and are arranged along part of the maxilla in an even series in a line measuring 16 mm. They are slender towards the tip, which is inwardly curved; they widen rapidly to the base, and in the alveolar socket are broad and cylindrical, as seen where a tooth has fallen out.

Length of teeth, 4 mm.; total length, with alveolar base, 6 mm.; width near base, 1 mm.

Squamation.—One of the highly important and interesting structures in Eothyrsites is the more or less complete scaly armour of the body. So distinct is this feature that, on first acquaintance with the specimens, it appeared as if the relationship to Thyrsites might be questioned. Upon examining the skin of a living Barracouta, it was seen that cycloid scales, precisely of the same character, and often of the exact dimension, of those in the fossil form Eothyrsites, were present along the lateral line of the fish, forming a close protective armature. It therefore seems entirely reasonable to suppose that in Eothyrsites we have an Oligocene form ancestral to the living Thyrsites and other related and almost scale-less fishes, as Lepidopus. In the case of Thyrsites a degeneration of the skin armature has taken place, the skin still being marked, however, by scale-like areolae, in which a vestige of the earlier scaly character has been retained for the protection of the slime canals. The average diameter of the scales in Eothyrsites is 4 mm., although in some cases they measure as much as 7 mm.; in Thyrsites the scales measure from 1.5 to 3 mm. The scales in Eothyrsites appear to be strengthened by ganoine and more or less calcified, whereas in Thyrsites they are thin and flexible.

The occurrence of the definite system of cycloid scales along the lateral line in the living Thyrsites does not appear to have been recorded by any previous writers excepting McCoy (1879), who says “greater part of the body naked” (loc. cit. p. 19).

Observations.—In its skeletal form the genus Thyrsitocephalus represented by T. alpinus vom Rath, resembles Eothyrsites. The former fossil, however, does not show the squamose characters, so that it seems safer to institute the new genus for the New Zealand specimen. Vom Rath's type of Thyrsitocephalus came from the Oligocene of Canton Glarus, Switzerland (Rath, 1859, p. 114, pl. III, fig. 4).

Locality and Horizon.—Marl Pit, Burnside, Green Island, near Dunedin, New Zealand. Upper Oligocene.

Note.—In my monograph on the Cretaceous and Tertiary Foraminifera of New Zealand (Chapman 1926, p. 16) I gave the horizon of the foraminifera of the Burnside marl as “Upper Eocene probably).” From a recent examination of the recorded fauna, together with additional foraminifera found by Miss Crespin and myself in the matrix with the fish skeleton, we find that it exactly agrees in the faunal horizon of the Goon Nure Bore, Gippsland, Victoria, below 2020 feet, which we have referred to the Upper Oligocene.