F. R. Coivper Reed — Notes on Trimicleus. 351 



furrows (the first lateral pair) indenting the base of the sides of the 

 pseudo-frontal lobe close to the axial furrows ; a weak, narrow 

 depression runs obliquely inwards and backwards from these 

 indentations to the second pair of lateral furrows, which are 

 represented by large isolated pits at the base of the pseudo-frontal 

 lobe ; the third pair of pits lie in the same longitudinal axial line as 

 the second pair ; a short arched furrow runs back from each of these 

 third pits, ending on each side in a deep but smaller pit in the 

 meso-occipital furrow, so that a fourth pair of pits is here present. 

 The short curved furrows between these third and fourth pairs 

 embrace between them a slightly swollen basal ring, forming the 

 posterior end of the incipient stalk of the glabella. Outside and 

 between the third and fourth pairs of pits, there is usually a small 

 pit of somewhat uncertain significance, but perliaps representing the 

 outer ends of the third lateral furrows, as it seems to lie in the axial 

 furrows. The true meso-occipital ring extends laterally outside the 

 above-mentioned basal ring, thus proving that the true base of the 

 glabella is wider than this ring, and, therefore, than the stalk of 

 the glabella ; and we are thus prepared to find portions of the glabella 

 on each side of the stalk, and to look further out for the posterior 

 course of the axial furrows. 



The axial furrows are seen to hold at their anterior ends the small 

 pits which have been erroneously ' considered to be for the insertion 

 of the antennae,' and may therefore be called pseudo-antennary pits. 

 From these pits they curve gently outwards with a slight convergence 

 posteriorly to the first lateral furrows, but behind them they become 

 gradually weaker, though distinctly traceable for fully three-fourths 

 of the way back to the base of the head-shield, separating the suddenly 

 rising cheeks on the outer side from elongated slightly convex areas 

 on the inside extending from the first lateral pits to the meso- 

 occipital ring, but depressed below the level of the median portion 

 of the glabella — the incipient stalk. These areas are the composite 

 lateral lobes, now merely indented on their inner sides by the pit-like 

 second and third lateral furrows, but bounded externally by the 

 axial furrows. The posterior ends of the axial furrows are almost 

 obsolete, but their position is marked on each side by a notch in 

 the posterior margin of the head-shield and by the junction of the 

 meso-occipital and pleuro-occipital rings. 



We thus see distinctly that the glabella in this species consists of 

 (1) a pseudo-frontal lobe, (2) a median posterior stalk-like portion, 

 and (3) a pair of elongated composite lateral lobes. 



We also note that there are three pairs of segmental furrows, of 

 which the second and third pairs are represented by more or less 

 isolated pits not connected with the axial furrows ; and that the third 

 pair is connected with a fourth pair of pits lying in the meso-occipital 

 (but not in the axial) furrows, leading to the formation of a basal 

 transverse swelling or ring. 



Finally we note the incipient obsolescence of the true axial furrows 

 behind the first lateral furrows. All these features we find reproduced 



^ Oehlert, Bull. Soc.Geol. France, ser. Ill, vol. xsiii, p. 302, 1895. 

 - McCoy, Syn. Silur. Foss. Irel., 1846, p. 42. 



