24 DEVONIAN FAUNA. 



Articulation to the thorax assuming the form of a less elevated ring, with a 

 central tubercle. Limb convex centrally, but becoming definitely concave near the 

 border, which is raised and linear ; bearing seven ribs divided into two elements, 

 of which the anterior is indistinct and vanishing, and the posterior sharp, narrow, 

 and becoming stronger and reflexed as it crosses the concavity to the border, 

 which it reaches, thus dividing the tail into wide triangular hollows. 



Size. — 5 mm. long, by 10 mm. wide, and 3 mm. high. 



Locality. — Lummaton. There are two specimens in my collection ; and another, 

 obtained by Prof. Hughes' party, is in the "Woodwardian Museum. 



Remarks. — I should not have regarded these curious little fossils as belonging 

 to the genus Proetus, were it not that they bear a very close resemblance to some 

 very rare Bohemian species which Barrande has described from their pygidia, and 

 has referred to it. They differ very widely from its more ordinary types of tail, 

 and when further portions of the animals are found it is quite possible that it may 

 become necessary to remove them from it. At present, however, I know no other 

 genus to which they could be united, and the material at hand is altogether too 

 scanty to form a new one. In the slightly " bottle-neck " shape of the axis and 

 the sharp distant ribs reaching the margin, they present some analogies to 

 Dalmanites, but in that genus the segments are generally much more numerous, 

 and the tail acuminate. 



We might, perhaps, trace some faint similarities to the distant family of the 

 Asaphidse, but the most interesting resemblance is to the Bronteidse, to which the 

 contour of the limb, the number of the ribs, and the tilted margin give a slight, 

 but not insignificant approximation. 



Of the Bohemian species by far the nearest to our English fossil is Proetus 

 gracilis, Barr., 1 which approaches it in most particulars, and is evidently closely 

 allied, but may be distinguished by its greater convexity, its closer ribs, the 

 anterior portions of which are more rudimentary and the posterior parts not so 

 strong laterally, and by its less elevated margin. P. insequicostatus, Barr.' 2 has a 

 much broader axis, a depressed margin, and the two elements of the ribs equally 

 elevated ; P. natator, Barr., 3 has a shorter axis and fewer and more obscure ribs ; 

 and P. latens, Barr., 4 and P. eremita, Barr., 6 have also a shorter axis with fewer 

 ribs and a depressed margin, and are granulated. 



1 1852, Barr., « Syst. Sil. de Boh.,' vo). i, p. 449, pi. xv, figs. 47—49, Et. F. and G. 



2 Ibid., p. 449, pi. xv, figs. 45, 46, Et. F. 



3 Ibid., p. 460, pi. xvi, figs. 36, 37, Et. F. 

 * Ibid., p. 451, pi. xv, figs. 52, 53, Et. F. 

 5 Ibid., p. 462, pi. xvii, figs. 9, 10, Ft. F. 



