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BY JOHN MITCHELL. 537 



basal lobes. Anteriorly the facial sutures run from the front of the eyes straight 

 to the inner edge of the thickened margin, thence inwardly, passing out at a very 

 acute angle; posteriorly, they extend from the inner angles of the eyes obliquely 

 and pass out near the fulcral angles. 



Thorax composed of nine segments, sides subparallel, much wider than long 

 (15.6 : 9.4), length equal to that of the pygidium or of the cephalon, which are 

 approximately of equal length. Axis prominent, spread nearly equal through- 

 out, much wider than one side lobe (approximately 5 : 3) ; each ring bears 

 some seven nodules, three of which are very prominent, especially the central 

 one, which is also subspinate, a feature of the central node on ea,eh ring, giving 

 to the axis a subserrated aspect, more pronounced on the axis of the pygidium. 

 Pleural lobes slope mildly from the axial furrows to the fulcral angles and thence 

 steeply to their margins; the medial furrow of each pleura is narrow and deep, 

 the posterior ridges, which are much stronger than the anterior ones, bear eight 

 or more nodules, of which that on the fulcral angle is most prominent and that 

 adjacent to the axial fun-ow nearly as prominent; the pleurae imbricate and 

 their ends have a slight forward trend. Axial furrows only moderately defined. 



Pygidium semi-elliptic, strongly convex and tuberculated. Axis very pro- 

 minent, consisting of fourteen or fifteen rings and terminating prominently and 

 bluntly before reaching the margin; the rings are tuberculated in a similar way 

 to those of the thoracic axis, but the central ones of the pygidium are more 

 spinate and recurved than are the similar ones of the thoracic axis and, in con- 

 sequence, when viewed from the side, the pygidial axis has a more serrated aspect 

 than has the axis of the thorax; these tubercles are arranged so as to form longi- 

 tudinal rows, both on the axis and on the pleurae, which is also a feature of the 

 tuberculation of the thorax. On the space between the end of the axis and the 

 margin are a number of tubercles similar to those which are on identical positions 

 of several species of Brachymetopus. 



Side lobes are made up of nine pjeurae in each, are strongly convex, slope 

 steeply from the fulcral angles to and across the mildly thickened borders, where 

 their ends are slightly depressed and tuberculated; on each pair of pleurae, ex- 

 cept the last, the medial sutures are narrow "but distinct; the posterior ridges 

 bear large bead-like tubercles, eight in number on the anterior pleurae, but 

 gradually decreasing to two or three on the ridges of the posterior pair; the 

 anterior ridges also bear rows of smaller tubercles, those on the posterior ridges 

 being so placed as to form longitudinal rows, the most conspicuous of which is 

 that along the fulcral angles; the border is ill-defined, except posteriorly, and 

 when it breaks away along its suture, which is not frequent, the under surface 

 is seen to be striated; axial furrows distinct. 



Dimensions: Leng-th, 28 mm., width across the genal angles, 18 mm. From a 

 specimen of which a longitudinal half is almost perfectly preserved, it is found 

 that the cephalon, thorax and pygidium have approximately the same length. In 

 both the thorax and the tail, the proportion of the width to the length is 2 : 1. 



The determination of the generic position of this trilobite has proved to be 

 a difficult problem. It does not fit either of the Carboniferous genera, and it 

 therefore becomes a question to decide whether it possesses generic features 

 sufficiently characteristic to justify the establishment of a new genus for its 

 reception. 



It seems impossible to place it in the genus Plnllipsia because on no cep- 

 halon of the many of the type examined has a trace of either medial or anterior 

 glabellar furrows been noticed. ■ It resembles Pliillipsia in the shape of its 



