AGNOSTUS OALLAVBI. 25 



on ;i somewhat higher horizon in Sweden. Tt agrees with this throughout in its 

 general character, but is widely different in its proportions. A. dux is broader 

 throughout, and the head- and tail-shields are rounded laterally; its axes, both of 

 head and tail, are much shorter; its marginal furrowis much shallower and farther 

 from the margin ; the furrow across the glabella is nearer the front; the anterior 

 furrow across the tail-axis is arched, not straight; and the tail-spines are not 

 directed outwards as in A. sidenbladhi. 



" A. dux closely resembles Angelin's figure of A. lentiformis, 1 Aug., in general 

 shape, differing chiefly in its shorter axes and the presence of the glabellar furrow 

 and tail-spines. It is also similarly close to Ins allied form A. glabratus, Aug.," and 

 still more so to that figured under A. glabratus var. ingrica by V. Schmidt, 3 from 

 which it differs in that both its bead and tail narrow towards the thorax, and both 

 are more rounded, while the glabellar furrow is stronger and farther forward. 



" The head of J. dux agrees exactly with the description of A. bavaricus; Barr., 4 

 which comes from the same or nearly the same horizon, with the exception thai 

 A, dux is much broader in proportion. Its relations with the new species 

 A. callavei, found associated with it in Shineton Brook, are noticed under that 

 form. 



" Type. — The original of Callaway's figure is in the Museum of Birmingham 

 University. The external cast of this specimen is in the Sedgwick Museum, 

 Cambridge. 



" Horizon and Localities. — Tremadoc : several specimens having been found in 

 the Shineton Shales at Shineton by Dr. Callaway and by Mr. R. Rhodes for the 

 Geological Survey at 18 — 20 chains S.W. of Shineton Church. It is also recorded 

 by Prof. T. Groom from the grey shales of the southern Malverns." 



22. Agnostus callavei, F. Raw, MS. Plate TT, fig. 20. 



For the following description and notes on this species I am again indebted to 

 Mr. Frank Raw. 



"Head roughly circular in outline, but broader than long ; marginal furrow very 

 shallow, genal angles rounded. Cheeks smooth, convex, narrower round the front 

 of the glabella. Glabella two thirds the length of the head-shield and one third 

 the width, well defined by sub-parallel axial furrows, round in front, widening 

 behind, with the posterior angles cut off by oblique narrow grooves; bearing an 



1 Pal. Scand., p. 7, pi. vi, fig. 6. See also Wiman, Arkiv. I\ Zool., to! ii. no. II (1905), pi. i. 

 figs. 21, 22. 



2 Angelin, op. cit., j>. 6, pi. vi, fig. 5. Wiman, he. cit., pi. i, figs. 27. 28. 



s Revision d. Ost-Baltiscben Trilobiten, pt. iv. (1894), p. 90, pi. vi, figs. 39 M. See also 

 Wiman, /<"■. cit., pi. i. figs. 23,24. 



1 Faune silurienne des environs .1.' Eof, en Baviere, p. 82, fig Hi 



I 



