F. R. Cowper Reed — On Phacops Weaveri, Salter. 73 



different state of preservation to those from tlie Tort worth district 

 and are somewhat crushed, distorted, and imperfect, so that their 

 identity with Fh. ]Veaveri must be regarded as doubtful. The larger 

 specimen of the pygidium (op. cit., fig. 8) shows 10 complete and 

 distinct rings on the axis followed by 4 or 5 small and very weak 

 rings ; the lateral lobes possess 9 distinct ribs, of which the first 

 8 correspond with axial rings ; the margin is not preserved and 

 the border is broken. The smaller specimen (fig. 9), except for the 

 presence of a short mucronate extremity, has practicalh^ all the 

 characters of the Tort worth typical form. Probably these Marloes 

 JBay specimens may be regarded as a local variety, but the material 

 is too indifferent and scanty for the satisfactory decision of this point. 



From the above detailed re-examination of all Salter's figured 

 specimens which he referred to one species, Ph. Weaveri, we find 

 that his definition of this species requires emendation, and though 

 we cannot give a precise and full description of the head-shield, yet 

 with regard to the pygidium on which the species was founded the 

 following summary of its characters may be substituted : — Shape 

 parabolic, wider than long, rounded behind, not mucronate; border 

 smooth, of subequal width all round, not produced into a point. 

 Axis conical, tapering regularly at about 20°-25° to obtuse tip, 

 annulated for whole length, with 8 complete strong rings 

 corresponding to the ribs, followed by 4-7 much narrower weaker 

 rings. Lateral lobes gently convex and arched down, composed of 

 8 slightly curved ribs, successively decreasing in size posteriorly and 

 the last pair subparallel, marked by fine submedian furrow for 

 greater part of length, separated by narrow interpleural furrows, 

 ribs and furrows ending abruptly inside border. (Figured by Salter, 

 Mon. Brit. Trilob., pi. iv, fig. 7.) 



This is the common species of Phacops in the Llandovery rocks 

 of the Tortworth area. I have examined a large series of specimens 

 collected by Professor S. H. Reynolds from the Llandovery Beds of 

 this area in the course of his stratigraphical work, and they are all 

 of the type of Phacops Weaveri as here defined. Excellent pygidia 

 from Daraery Bridge, Daniel's Wood, and the site of Long's Quarry 

 agree precisely with those from Long's Quarry used by Salter in 

 drawing up his inaccurate diagnosis, and with the specimen accurately 

 figured in his monograph (pi. iv, fig. 7). There is, therefore, not 

 the least doubt now as to the true characters of the pygidium, and it 

 has been above shown that it is on this member of the body that 

 the species rests. The new and emended definition which I have 

 here given must accordingly be in future regarded as expressing the 

 specific characters of Ph. Weaveri. As regards its systematic position, 

 it must be placed in the subgenus or section Bahnanitina proposed 

 hy the author in 1905 ^ for certain members of the genus Dalmanites, 

 if we separate the latter generically from Phacops, as seems justifiable 

 and natural, though this practice has been rarely adopted by European 

 palaeontologists. 



' Eeed, Geol. Mag., Dec. Y, Vol. II, 1905, pp. 172-178, 224-228. 



