312 Notice of the u Silurian System of 



species would reward his toil. As a stimulus to geologists 

 in other little explored regions, we may mention, that whilst 

 Bohemia, previous to his time (1840), had only furnished 

 twenty-two species of palaeozoic fossils to science, he has 

 now raised the number to 1200 species, most of them fully 

 represented by numerous fine specimens. 



The very high value of M. Barrande's researches, both in a 

 zoological and geological point of view, will perhaps be best 

 indicated by a brief notice of some of their results. He com- 

 mences with a general account of the component elements of 

 the body of the trilobites. In this he notices the broad and 

 long forms which the various individuals of each species pre- 

 sent, and which seem to correspond to the two sexes, — the 

 males represented by the long, the females by the broad 

 specimens. He also confirms Mr Salter's observations, that 

 the former are besides indicated by more prominent eyes, 

 and by numerous points, spines, or other ornaments on their 

 shell, similar to what is well known to occur in insects at the 

 present time. He then notices each of the three segments 

 of the body — the head, thorax, and pygidium or tail — in suc- 

 cession. On the head, he describes its general contour, the 

 form of the glabella or median lobe, and of the furrows by 

 which it is bounded. The sutures or joints by which the 

 cephalic carapace is divided into several distinct pieces, are 

 fully explained, and illustrated by figures of those observed 

 in the forty-five genera he has studied. These joints have 

 not been noticed in the recent Crustacea, and were probably, 

 as Burmeister thinks, intended to facilitate a slight motion 

 in the pieces when the animal rolled itself up. 



The eyes of the trilobites have always been regarded with 

 much interest. He has found these organs in many species 

 formerly supposed to be destitute of them ; but a few genera, 

 as Agnostus, Ampyx, Dindymene, and Dionide, shew no trace 

 of eyes; whilst in Conocephalites and Trinucleus some species 

 possess and others want them. Singularly enough, all these 

 genera belong to the lower Silurian rocks ; whereas only one 

 species (of Ampyx) destitute of eyes has been hitherto ob- 

 served in the upper Silurian stages. In one species, the 

 Trinucleus Bucklandi, the eyes seen in the young specimens 



