50 CARBONIFEROUS TRILOBITES. 



from it in the number of lateral articulations, which are from eleven to twelve, 

 instead of nine. Secondly, by the mode of their double furrow which gives rise to 

 ribs of unequal length, and also because these articulations are nearly united behind 

 the median lobe, and not separated by a broad obtuse palette as in our species." 



A pygidium of this species was first observed in 1844 by Prof, de Koninck 

 in Belgium, but he erroneously referred it to Ph. Jonesii, of Portlock, which is 

 a true Phillipsia, and has since been placed as a synonym under P. derbiensis. 

 A second pygidium was next observed in the Carboniferous Limestone of Russia 

 by M. de Verneuil, who named it, in 1845, P. ouralica, M'Coy, having in 1847 

 established the genus Brachymetopus for certain other closely similar forms. Prof. 

 Morris, in 1S54, placed both de Koninck's P. Jonesii and De Verneuil's P. ouralica 

 together under Brachymetopus, giving de Verneuil's name the priority (the name 

 Jonesii being a synonym of P. derbiensis, and therefore disqualified for use). I cannot 

 ascertain certainly whether Sir R. I.Murchison published the 1 854 edition of ' Siluria' 

 prior to the second edition of Morris's Catalogue (1854) or not, but at p. 283 Murchi- 

 son gives on his woodcut of Fossils (5G) fig. 1, a head-shield of a Carboniferous 

 Limestone Trilobite, named Brachymetopus ouralicus. Morris no doubt obtained 

 his knowledge of the occurrence of this species in England from Salter, whom he 

 quotes as his authority (at p. 101, op. cit.) C. L. Derbyshire {Salter). Murchison's 

 woodcut, although very small, is, however, more like the head-shield of B. Maccoyi, 

 having the cheek- spines more prolonged than is observed in B. ouralicus. 



In Salter's and Woodward's ' Chart of Fossil Crustacea ' (1865) Mr. Salter 

 figured a head-shield under the name of B. ouralicus, in which no cheek-spines are 

 shown at all. This was probably reproduced from a damaged specimen, as 

 B. ouralicus always seems to have very short cheek-spines. 



In 1867 Valerian von Moller figured a head of Brachymetopus, from the Ural 

 Mountains, which he placed under B. ouralicus with a note of interrogation, and 

 he makes the following observations upon it (op. cit., p. 27). 



"Brachymetopus uralicus was first described by De Verneuil as Phillipsia 

 ouralica in the year 1845, but De Verneuil knew only the tail-shield. A few years 

 later a cephalothorax was found in the Carboniferous Limestone of Derbyshire, 

 which showed by its head decoration that it was so nearly related to De Verneuil's 

 species that English palasontologists did not hesitate to identify it with that 

 species. On the other hand, the English specimen shows in the principal features 

 a marked resemblance to P. Maccoyi, Portl., so that no doubt now remains as to 

 its connection with Brachymetopus. Under this generic name the fossils of our 

 own country were first made known in Morris's ' Catalogue of British Fossils,' 

 and later in Murchison's ' Siluria ' (both in 1854). The result of the last year's 

 researches decides me still more in the conclusion that the specimen from 

 Derbyshire quite differs from the typical Uralian form, and therefore belongs to 



