150 MR. P. P. COWPEP PEED ON THE PATTNA OF THE [May IQO9, 



T. bicuspis, Angelin, 1 but no pair of anterior spines has been 

 observed in any of our specimens. The shape of the glabella, 

 relatively wider cheeks, and absence of a median occipital spine dis- 

 tinguish it from T. fr actus, Barr., which I have described 2 from the 

 Whitehouse Group in the Girvan district. 



SXMPHYSTTPTTS (?) sp. (PI. VI, fig. 12.) 



One interior of an imperfect head-shield from the Shangort Beds, 

 found south-south-west of Shangort, may doubtfully be referred to 

 Symphysurus or Nileus. The almost perpendicular course of the 

 posterior branch of the facial suture from the eye to the posterior 

 margin of the head-shield, the large prominent semicircular eye- 

 lobe, the narrowness of the fixed cheek, the shape of the glabella, 

 as evidenced by the course of the axial furrows running straight 

 forwards from the posterior margin to beyond the eye with a 

 slight concave outward curvature, and the marked independent 

 convexity of the wide subcylindrical glabella are features which 

 recall Symphysurus angustatus (Bceck). 3 Unfortunately, the front 

 part and left-hand side of the head-shield are missing ; and their 

 absence, coupled with the poor state of preservation of the rest of the 

 specimen, makes a satisfactory identification of the genus uncertain. 



Acrotreta (?) hibernica, sp. nov. (PI. VI, figs. 13 a, 13 b, & 13 c.) 



There is one pedicle-valve and its external impression from the 

 limestone of the upper part of Stream P (45), which may probably 

 be assigned to the genus Acrotreta, although its ornamentation 

 resembles that of Acrothele granidata, Linnarsson. 



The pedicle-valve is regularly oval, about one and a half times as 

 long as broad, gently convex and very obliquely conical ; the beak 

 is elevated, and the subapical pseudo-area is short and steep, with 

 a broad median shallow groove. The apex of the valve being broken 

 off, it is uncertain whether a foramen was present. The ornamen- 

 tation of the surface is very well preserved, and is a conspicuous 

 feature ; it consists of fine, concentric, somewhat irregular lines, 

 elevated at close intervals into small elongated papilla?, which are 

 very minute near the apex but increase regularly in size in the 

 successive concentric rows to the margin. An obscure alternate 

 arrangement of the papillae is here and there observable, but for 

 the most part they are irregularly placed, though closely set. 



Dimensions. — Length = 8 millimetres; width = 5 mm.; height = 

 about 2 mm. 



Species of both Acrothele (A. granidata, Linnarsson) and of 

 Acrotreta have been recorded by Davidson * from the British and 



i N. P. Angelin, ' Palssont. Scand.' 1854, p. 91 & pi. xli, fig. 22. 



2 F. Pi. C. Reed, ' Lower Palasozoic Trilobites of Girvan ' pt. i, Monogr. 

 Palseont. Soc. vol. lvii (1903) p. 44 & pi. iv, fig. 11. 



3 W. 0. Brogger, ' Die Silur. Etagen 2 & 3 im Kristianiagebiet, &c.' 

 (Christiania, 1882), p. 60 & pi. iii, figs. 9-9 a. 



4 T.Davidson, ' Monogr. Brit. Foss. Beach.' vol. iii, p. 343 & pi. xlix, figs. 3G-40. 

 Palaaont. Soc. vol. xxiv (1870) ; Suppl. vol. v, p. 213 & pi. xvi, figs. 21-23 

 (Acrotreta nicholsoni) ; Suppl. vol. v, p. 214 & pi. xvi, figs. 29-30 (Acrothele 

 granidata), Palajont. Soc. vol. xxxvii (1883). 



