&2 TRILOBITES OF GIRVAN. 



at about 45°. Shallow groove behind the fulcrum. Axis well marked, short, 

 triangular, about one third the length and less than one fourth the width of the 

 pygidium. Axial furrows distinct, straight, converging at angle of about 60° 

 to meet at tip of axis. Fascia round posterior margin strong, concave, about one 

 third the length of the pygidium, marked with closely set concentric striae. 

 Ornamentation unknown. 

 Dimensions.— 



Width of head-shield (about) . . . 3(3'0 mm. 



Length of „ . . ?14-0 „ 



Width of glabella between eyes . . . 5"0 „ 



Length of thorax . . . . 8"0 „ 



„ of pygidium . . . . 13*5 „ 



Width of . . . 20-0 „ 



„ of axis of pygidium . . 6*5 „ 



Remarks. — An almost complete individual and an external impression of the 

 same are the material on which this new species is founded. Both were obtained 

 from the Starfish Bed (IT. Bala), and are in Mrs. (I ray's collection. 



A small epistome of an lllsenus from the Starfish bed is also probably referable 

 to this species. Its description is as follows : — Shape transversely fusiform, 

 anterior margin gently arched forward ; lateral angles obliquely truncated at 

 about 00° to front margin; posterior margin obtusely angulated in centre, forming 

 slightly swollen median projection; ornamented with 8 — 10 strong strias from side 

 to side. Dimensions. — Width between lateral angles, 11 mm. ; length from back 

 to front across middle, 5 mm. 



Affinities. — The elevation of the eye-lobes and of the median portion of the fixed 

 cheeks recalls J. tauricornis, Kutorga; ' the pointed genal angles, the triangular axis 

 and straight front margin to the pygidium resemble I. schmidti, Nieszk., 2 but the 

 peculiar neck-ring, smaller eyes, narrower glabella, narrower axis and wider 

 pleurae distinguish this Girvan form from both these species. 



The species which appears to bear the closest resemblance is I. waMenbergianus, 

 Barrande, 3 which possesses a glabella of similar shape, spinose genal angles, pleurae 

 and axis of similar proportions and characters, pits at the base of the pleura? in the 

 axial furrows, pygidium of much the same shape and an axis of the same relative 

 width and length. But there is no neck-ring, the eyes are larger, the cheeks less 

 elevated and the pygidial axis less defined. 

 Collection. — Mrs. Gray. 

 Horizon "ml Locality. — Drummuck Group (U. Bala): Starfish Bed, Thraive Glen. 



1 Kutorga, ' Einige bait, silur. Trilob.' (1848), p. 42, pi. viii, figs. 1 a — c, 2 a. 



- Nieszkowski, ' Archiv Naturk. Livl. Ehst. Kurl.,' ser. i, vol. i (1857), p. 580, pi. i, figs. 10—12. 



3 Barrande, ' Syst. Silur. Boheme,' i. p. 684, pi. xxxiv, figs. 19 — 25. 



