KONGL. SV. VET. AKADEMIENS BANDLINGAR. BAND 34. S:0 8. 23 



blind. We have not amongst hundreds of specimens of tliese genera found a single Bpe- 

 cimen showing an ocular globe covered with facets. Olenus and the aearlj related genus 

 Parabolina ;tre found in innumerable specimens in the thinly laminated aluinschists of 

 Scania and othcr provinc.es of Sweden. But rarely a perfecl head shield, or aearly so, 

 is to be found with the free cheeks in place. If so, the semicircular scallop in the free 

 cheek is entirely filled up by the posterior lobe of the facial ridge and there is no place 

 lett for any eye. — If we, again, find a tion compressed glabella and fixcd checks likeuisc. 

 the facial lobe (-»eye-lobe») is in sonie elevated so much as to leave a little space between it 

 and the scallop of the free cheek, which space must have been an empty lacuna if not 

 filled up by an eye ball. But it raay also be that the free cheek has been somewhai pul ou1 

 of its order and that consequently sonie space has been left between it and the IVcc elieek. 

 It is quite as niuch with older genera, as Solenopleura especially, in which the posterior 

 lobe of the facial ridge (vulgo »eye lobe») has attained a great development, and in which 

 one just could expect to find a sphaerical eye resting betAveen the elevated lobe and the 

 scallop. The elevated rim of this scallop does not in fact constitute a proof for its having 

 clasped an eye as the elevated scallop in Sphaerophthalmus did. In Paradoxides, again, in 

 Ellipsocephalus, where there is absolutely no trace of an eye ever having been present, 

 whenever you succeed to find the free cheek in juxtaposition with the fixed cheek it 

 is evident that the elevation of the scallop rim is due to the impact of the posterior 

 lobe of the facial ridge. In niany specimens of Dolichometopus and Corynexochus etc. 

 no free cheeks have ever been found and to judge by the shape of the facial ridge it 

 may be concluded that these also were deprived of eyes. 



On seeing this great number of trilobites, that on account of their organization 

 must be considered as blind, the first suggestion that strikes the mind, is that they must 

 have lived in abvssal depths of the Cambrian sea, where the most intensive darkness pre- 

 vailed. Nor does the nature of the strata contradict such an assumption as evidentlv 

 this fine sediment must have been deposited far beyond the reach of the influence of the 

 wave motion, a depth amounting to more than a thousand metres as now calculated, for 

 else it could not have preserved unbroken such delicate parts of organisms as that free cheek 

 of Ctenopyge pecten with its extraordinary long and delicate horn, figured on plate III fig. 

 27 and niany others. But it seems incredible that such a state of things should have 

 prevailed during the deposition of all the Cambrian strata, although they in Sweden 

 amount to only 160 feet in thickness, according to the evaluation of S. A. Tullberg, 

 not considering what has been löst through denudation. The length and duration in 

 time can in this instance not be measured by the thickness of the beds, but by the great 

 changes in the faunas which there have succeeded one another. The physical conditions, 

 to judge by the composition of the rocks, seem in the main to have lasted during ini- 

 measurable periods and still the fauna has changed in no little degree. During that enor- 

 mous length of time, embracing in Sweden eight well separated periods, there must, how- 

 ever, have been minor changes in the conditions of depth and consequently in the nature 

 of the depositions. To a certain extent the physical agents must have influenced the 

 organization of the animals, but not essentially. There are sure evidences of another 

 factor being the chief agent and that is the evolution. 



