AGNOSTUS PUNCTUOSUS. 



1879. Agnostus punctuosus (viir. bipunctata), Brogger, ibid., p. 08, pi. v, fig. 2 c. 



1872. Agnostus scutalis, Salter (pars), Hicks, Quart. Jouru. Geol. Soc, vol. xxviii. \>. 175. pi. v, fig. '.» 



and perhaps fig. 10. 

 1872. Agnostus scarabseoides, Salter, Hicks, ibid., p. 175, pi. v, fig. 8. 



1880. Agnostus punctuosus, Tullberg, Agnostus-artema, p. 17, pi. i, fig. 5 a — d. 



1896. Agnostus punctuosus, G. F. Matthew, Trans. N. Y. Acad. Sci., vol. xv, p. 232, pi. svi, fig. 11 a, b 



Head rounded, with narrow margin. Glabella nearly triangular, bilobed ; the 

 anterior lobe narrower than the posterior, triangular; posterior lobe large; basal 

 lobes elongated, triangular. Cheeks separated in front of the glabella by a furrow 

 (which is sometimes lost), surface granulate. 



Tail rounded, with narrow margin. Axis formed of three segments; the 

 anterior segment is wider but shorter than the others; the second narrower than 

 the rest, hexagonal, longitudinally keeled, the keel forming a projection at its 

 posterior extremity ; the third segment forms an elongated isosceles triangle, -with 

 its point directed backwards and its basal angles slightly rounded. Lateral lobes 

 granulate, united behind the axis, except in young specimens. 



Head- and tail-shields 4-5 mm. long and wide. 



The head of this species is easily distinguished from that of most other British 

 forms by the triangular shape of the anterior lobe of the glabella and the scrobiculate 

 surface of the cheeks. A. pisiformis possesses the former of these two characters, 

 but its cheeks are smooth, the basal lobes are smaller, and the whole glabella is 

 less nearly triangular in shape. 



The tail is easily recognised, even in poor specimens, by the elegant shape of 

 the axis, narrow at the second segment, immediately afterwards, at the base of the 

 third segment, widening, and then tapering regularly to a rather sharp point. The 

 axis of the tail of A. exaratus is somewhat similar in outline, but in that form there 

 is no trace of segmentation, and the axial and marginal furrows and also the furrow 

 behind the axis are all very deep. 



Synonymy. — Agnostus xcarabseoides, Salter, as described by Hicks, is clearly 

 only a flattened and somewhat imperfect specimen of this species. In all the 

 characters which it shows it agrees precisely with the Scandinavian form, excepting 

 only that it is wider in proportion to its length, and this is apparently due to the 

 flattening of a form which is most convex transversely. The original of Hicks's 

 figure shows no furrow in front of the glabella, but this furrow is not always very 

 distinct, even in the Swedish specimens of A. punctuosus, and might easily be 

 obscured in a poorly preserved specimen. 



The specimen figured by Hicks as the tail of Agnostus scutalis in 'Quart. Journ. 

 Geol. Soc.,' vol. xxviii, pi. v, fig. 9, is a beautiful tail of Agnostus punctuosus — 

 probably, from its small size and the presence of a furrow behind the axis, a young 

 individual. The specimen shown in fig. 10 of the same plate is probably a still 

 younger stage (cf. Tullberg, ' J^os^s-arterna,' pi. i, fig. 5 c). 



