74 TRILOBITES OF GIRVAN. 



Dimensions. — 



I. II. 



Length of head-shield . . 30'0 mm. 20*0 mm. 



Width of . . 45-0 „ 30-0 „ 



Collection. — Mrs. dray. 

 Horizon and Locality. — Stinchar Limestone Group (Llandeilo) : Craighead. 



Family Proetid.e. 

 Genus PROETUS, Steininger. 

 1. Proetus girvanensis, Nicholson and Etheridge, 1879. Plate XI, figs. 1 — 3. 



1879. Proetus girvanensis, Nicholson and Etheridge, Mon. Silur. Foss. Girvan, fasc. ii, p. 169, pi. xii, 



figs. 7—10. 

 1899. Proetus girvanensis, Mem. Geol. Surv., Silur. Rocks Brit., vol. i, Scotland, pp. 524, 673, 689. 



Specific Characters. — General shape oblong oval, tapering slightly posteriorly. 



Head-shield subparabolic in appearance rather than semicircular, owing to the 

 sides being bent down ; convex from side to side and from back to front ; about 

 twice as broad as long. Border surrounding head narrow, band-like, marked off 

 by fairly strong furrow. Glabella short, wide, nearly as broad as long, narrowing 

 a little anteriorly and slightly contracted in front of basal lobes ; anterior end 

 bluntly rounded, nearly reaching anterior border. Lateral furrows distinct l and 

 consisting of three pairs ; the two anterior pairs short, fine, weak, nearly horizontal 

 and parallel, the front pair very far forward, being nearly at the anterior 

 lateral angles of the glabella, and the second pair opposite the anterior end of the 

 eyes ; the third or basal pair of furrows opposite the middle of the eyes and running 

 obliquely back to the occipital furrow, thus marking off a pair of triangular basal 

 lobes on the glabella, each rather less than one third its basal width. Axial 

 furrows deep, well marked, converging a little anteriorly, and uniting in front of 

 glabella. Occipital furrow deep, arched forward in centre and bent up at sides. 

 Occipital segment wide, flattened, with central tubercle and almost obsolete, small, 

 indistinct occipital lobes. Fixed cheeks very narrow, uniting in front of glabella 

 as strongly convex narrow band. Palpebral lobes rounded, of moderate size, gently 

 upturned, situated opposite middle of glabella and extending more than one third 

 its length. Facial sutures cutting front margin of head outside anterior lateral 

 angles of glabella, running back thence straight to eyes, and behind it running 

 straight back till opposite occipital furrow, where they suddenly bend outwards 



1 According to Nicholson and Etheridge they are indistinct, and no description of them was 

 given by these authors ; but even in the type specimens they are clearly seen, though the shell is not 



