216 



SILURIAN TRILOBITES. 



We next take up the Bronteidce, a small group in Britain, but a very large one on 

 the Continent. They are closely allied to the Ogygides through Barrandia. 



Yi.^\\.\~BItONTEIBM, Barrande, 1852. 



If M. Barrande did not actually add the family termination to the name, he showed 

 clearly that Bronieus constituted a family group distinct from any other. Originally 

 confounded with AsapJius (or rather lUmius) by Brongniart, the generic rank of Bronteus 

 was perceived by Emmerich, and seized upon by the diligent Dr. Goldfuss, who named 

 the genus in 1839. The name Brontes had, indeed, been previously applied to one of the 

 Coleoptera, and it is against all rule to admit a double employ of the same name in 

 zoology. Yet Dr. Koninck's proposition to honour the Bonn Professor by the term 

 Goldius has met with no concurrence, and the original name is still preserved. 



Dr. Beyrich, who described several of the species first, was the earliest to perceive the 

 necessity of subdividing the cumbrous genus. His view of its relations was not so clear, 

 for he endeavoured to unite it with the Cheiruridce, to which, indeed, as Barrande has 

 pointed out (and, indeed, he seems half inclined to follow the Dr.'s suggestion), the 

 analogies are close. The granulated eye, the short axis and radiated pleurae of the tail- 

 piece, no doubt suggested this comparison to the naturalist who was the first to accurately 

 describe both genera. But there is, I think, no real affinity between them. 



The true relations of Bronteus are, as Prof. M'Coy perceived, with the Ogygince, but 

 it is through forms which were not accessible to Beyrich or Emmerich. I shall not 

 notice the fanciful and absurd division of the genus by Corda ; but follow Beyrich, as 

 Barrande has done, in arranging the species according to the number of segments 

 combined in the pygidium. This is not usually a part of much consequence in classi- 

 fication ; but by tracing the variation of the tail-piece in Bronteus, through Bronteopsis to 

 Barrandia, the relations of the group to Ogygia are clearly seen. Otherwise we should 

 really have had to look for its affinities to Cheirurus, as Beyrich has done. But the rostral 

 shield and ungrooved pleurae are as much characters of Illanus as they are of Cheirurus. 

 The granulated eye is found, it is true, in ^glina ; but it is very rare in the Asophida. 

 The shape and lobes of the glabella are much like those in Barrandia ; and, as before 

 said, the shortened tail-axis of the last genus points to the still shorter axis in Bronte- 

 opsis, and the almost obsolete one in Bronteus. 



We may define the forms in this family as follows : 



Broad oval, generally depressed, sometimes very convex, with nearly equal head and 

 tail portions ; liiieatcd (rarely granulated) all over. Glabella distinct and wide above, with 

 three luicqual lateral lobes and a broad large forehead-lobe ; a rostral shield ; granular 

 eyes ; the facial suture ending on the posterior margin ; ten groovelcss pleurae. The tail 

 large, with greatly abbreviated axis and radiant pleurae. 



