XX.— Two New Trilobites from Girvan

Abstract

The purpose of this short paper is to put on record 2 new species of trilobites from the Ashgillian rocks of Girvan. The specimens were found by the writer and the new Proetid is described by him. The new Illaenid has been described by Dr. Reed of Cambridge who has contributed so extensively to our knowledge of the fauna of the Lower Palaeozoic rocks of the Girvan District. The new Proetus comes from the ‘Upper Starfish Bed’ (Bed No. 2), which is 18 inches higher than the older well-known “Starfish Bed” (Bed No. 1) in the Drummuck Group of Lady Burn. This upper bed has yielded 5 new species of Proetus none of which has been found in the lower bed. The new Illaenus is from the lower bed (No. 1) and as will be seen in Plate 1, figs. 3, 4, the anterior margin of the doublure or reflexed border is composed of three curves, a feature which has been found in other Illaenids from the same horizon ( I. longicapitatus, I. fluvialis and? I. cf. avus ). J.L.B. Description of Species. Illaenus drummuckensis sp. nov. Plate 1, figs. 3, 4. Pygidium elongate, semioval, gently convex, most so transversely. Axial lobe indistinctly defined, nearly half the length of the pygidium, with slight independent convexity anteriorly, and projecting considerably beyond the anterior margin, more than one third the width of the pygidium. Pleural lobes gently arching down to undefined slightly concave border; short straight anterior edge; fulcrum at about one-third the width This 250-word extract was created in the absence of an abstract