BRACHYMETOPUS. 51 



some other species ; my reasons for this I will find an opportunity to give more 

 fully." 



At p. 67 he observes : " The cephalothorax under consideration is distin- 

 guished from the other species of Brachymetopus by the rounded cheek-plates, 

 the wide front, and by the smooth rounded border, and by a different distribution 

 of the bead-like ornamentation of the surface. I believe this specimen belongs to 

 the same species as the pygidium, which has been described as PhilUpsia ouralica 

 by De Verneuil ; at all events, both offer a great similarity in the ornamentation 

 of the surface. If time should prove that my idea is correct then the cephalo- 

 thorax from the Carboniferous Limestone of Derbyshire, figured in Murchison's 

 ' Siluria ' as Brachymetopus our aliens, belongs to a separate species. It differs 

 from the Ural specimens in the pointed cheek-spines, the remarkably small 

 glabella, and the conspicuously small eyes. 



In the last-mentioned characters the cephalothorax from Derbyshire differs 

 from all other Brachymetopi, and I think therefore that it belongs to the already 

 mentioned tail called PhilUpsia Jonesli of De Koninck. In Morris's ' Catalogue of 

 British Fossils,' 1854, p. 101, we find these Belgian specimens united with 

 B. ouralicus, but they differ from it in the club-shaped widened form of the tail- 

 segments, and the irregularity of the arrangement of the tubercles upon their 

 surface." 



It will readily be seen how the difficulty which von Moller experienced arose, 

 when we bear in mind the fact that de Verneuil's PhilUpsia (Br.) ouralica was 

 established upon a pygidium only ; and de Koninck' s PhilUpsia (Br.) Joncsii, 

 upon a similar tail from Belgium. M'Coy, who established the genus Brachyme- 

 lopus, did so upon the head and tail of another species, and makes no mention of 

 either the Russian or Belgian specimens. 



I think we are justified in concluding (a) that the small head-shield figured by 

 Salter in Murchison's 'Siluria' (1854) as B. ouralicus (p. 283, fig. 1, Fossils 56) 

 is most probably B. Maccoyi ; (b) that the figure in Salter's and Woodward's 

 chart of Fossil Crustacea (fig. 118, 1865) destitute of cheek-spines is a badly 

 drawn or imperfect shield of B. ouralicus; (c) that von Moller's figure of a head- 

 shield of B. ouralicus (?) is either quite a distinct species, without cheeh-spines, 

 and more highly ornamented, or that the Russian artist in Moscow who prepared 

 the plate may have embellished it a little more than the specimen perhaps 

 warranted, in placing the large tubercle on the centre of the glabella, in omitting 

 the basal lobes on the glabella, and giving the angles of the cheeks a rounded 

 contour. This last-named feature may be due to the fact that the check-spines 

 were not preserved ; of course, there may have been two forms, one with cheek- 

 spines, and one without. 



I think for the present, however, we may safely retain the name ouralicus for 



