F. R. Coicper Reed — On Phacops Weaveri, Salter. 71 



furnished with a mucro. The eight ribs of the lateral lobes corre- 

 spond with the first 8 rings of the axis, the posterior annulations of 

 the latter thus having no corresponding ribs. 



The head-shield from Long's Quarry (jSTo. 19223 in the Jermyn 

 Street Museum) which Salter figured in his monograph on pi. iii, 

 fig. 1, is imperfect on the left side. Its length is about 14 mm., of 

 ■which the frontal lobe of the glabella accounts for 8 mm. ; this lobe is 

 12 mm. in width and projects a little laterally, and has a well-marked 

 elongated pit in the median line, as Salter represented in his figure 

 hut did not mention. The first lateral lobe has a somewhat greater 

 length along the axial furrow than Salter's figure shows. The second 

 and third lateral lobes are of equal size. The first lateral fuiTow 

 runs inward at about 50°-60°, and the second and third lateral 

 furrows, which are parallel to each other, at about 7 0^^-76° to the 

 axial furrows. The eye-lobes are rather larger and longer and the 

 eyes rather less curved and rather nearer the glabella than in typical 

 examples of Ph. caiidatus, but except in these details there does not 

 appear to exist any marked difference. 



With regard to the pyg-idia, which Salter described and figured 

 (Mon., p. 58, pi. iii, figs. 2, 3) as the "larger form of the species", 

 from the so-called Ludlow rocks of Horse-shoe Farm, Tortworth/ 

 we may note several important points of difference from those just 

 discussed. Eoth are preserved in the same matrix and are considerably 

 larger than the others; one of them (op. cit., fig. 2), though imperfect, 

 possesses a length of about 25 mm., and is estimated to have had 

 a length originally of 38-40 mm. with a rather less width ; the other 

 (op. cit., tig. 3), which is also broken, now measures 35 mm., but 

 when perfect its length must have been at least 50 mm. Moreover, 

 from the contour of the margin near the posterior extremity of each 

 specimen there is every indication that the border was produced 

 behind into a mucro, though the length of the latter cannot be 

 determined. 



From the specimen represented in Salter's fig. 2 the shell is missing, 

 except near the right margin, where its surface is seen to be minutely 

 and regularly granulated. This is not shown in the figure or 

 mentioned in the text. Only the right half of the pygidium is present ; 

 the axis tapers very gradually so far as can be seen, and shows 15 

 distinctly marked rings with traces of a 16th, followed by a non- 

 annulated piece extending to the tip of the axis, and equal in length to 

 about the last four rings. The transverse furrows between the rings 

 are weak in the centre but deeply impressed at the sides. There are 

 13 ribs on the lateral lobe, counting the anterior marginal one, and the 

 first 11 ribs correspond with axial rings; the ribs are gently curved 

 back and are somewhat flattened on the surface, and are rather 

 broader than the wide interspaces or furrows between them. The 

 anterior face of each rib is obliquely bevelled, but the posterior face is 

 nearly vertical. The 2nd to 4th ribs have a very faint median 

 impressed line traceable along three-fourths of their length. The 

 last lateral rib is very short and weak, and lies nearly parallel to 

 the axis. 



1 Eeed & Eejiiolds, op. cit., p. 524. 



