210 



SILURIAN TRILOBITES. 



sculpture, of the front margin, the depth or shallowness of the axal fuiTOw : nor any 

 characters, other than length and breadth, of the pygidiura. StiU the two species 

 must be very near indeed. And both are remarkable among the Bumasti, for spinous 

 head-angles, a character which we do not know in more than a few instances, even 

 among the typical lllani. 



Locality. — Wenlock Limestone, Winnings Quarry, Malvern. (Museum Practical 

 Geol., and the late Mr. H. Wyatt-Edgell's Cabinet.) 



iLL^iNUS (BUxMASTUS) Maccallumi, u. sp. PI. XXVIII, fig. 1. PI. XXX, figs. 2, 3. 



//. [B) 2 uncias longm, capite obtuso, lunato, caudd suhtrigond. Caput gibboswn, 

 oculis majoribus. Thorax subtrilobus. Cauda par abolica, subtrigona fere, lavis : axis ejus 

 laius, ad marginem curvum tantum conspicuus ; latera fulcro valde prominente, axe 

 proximo, IcBvia, nisi sulco superno profundiore distincta. Fascia caudalis angusta, 



A few specimens only of this new species have occurred to the Geological Surveyors 

 in the course of their work at Girvan, Ayrshire ; and one or two, more complete, are 

 in Prof. Thomson's cabinet. One of his specimens (PI. XXX, fig. 3) shows nearly all 

 the body-rings and part of the head. Prom these we learn that the head was so convex 

 as to be almost hemispherical and blunt-edged, while the tail is very little gibbous, and 

 is pointed — an unusual character. 



The head seems to have been transverse, lunate ; most gibbous in front, Avith large 

 eyes proportionally, though they are somewhat less than in //. Barriensis, and placed 

 rather further back. The glabella-furrows curve quite round the eyes in front — incurved 

 and then recurved, as in the larger species. The central punctum on the vertex is 

 strong, and a ridge runs from it ; but the head is not otherwise at all keeled. Our 

 figure looks a little as if it were so. 



Thorax of ten ? very much arched rings, which show a very broad axis, as usual in 

 the sub-genus, but a more decided axal furrow than in our two Wenlock species. The 

 pleurae are short ; their apices rounded, and curved forward. 



The tail is very regularly but not highly convex — a long half-oval. It is one inch 

 long, and as broad at its upper curved margin, which shows distinctly the axal points, 

 distant from each other fully three fifths of the width of the tail, and deeply indented. 

 These are, however, not continued in anywise as furrows down the tail itself. Almost 

 immediately beyond these points the front margin rises abruptly to the prominent 

 fulcrum, and from thence descends to the contracted outer and upper angles ; a sharply 

 marked facet is still further defined by the subtending upper furrow, more strongly 

 indented in this than in any other Bumastus known. 



The surface of the tail is convex, somewhat gibbous down the central line, and tliis is 

 not due, except in part, to pressure in the arenaceous rock. From this central line the 



