135 



UPPER SILURIAN FOSSILS. 



By the Eev. ROBERT DIXON, m.a. 



"Et procul a pelago conchce jacuere mariiws." 



Ovid Metam, xv. 264. 



Our head quarters being in the immediate neighbo.u-hood of an upheaval 

 of Upper SUurian rocks, we have thought that we should further one of the 

 objects for which the Club was founded by giving some account of the 

 paleontology of this epoch, accompanied by some fossU sketches, the Central 

 Committee being singulai-ly fortunate in possessing artistic power to illustrate 

 its science. 



Deferring the consideration of the fish remains, found as yet in the 

 Ludlow series only, we shaU begin with the MoUusca, selecting for delineation 

 not only specimens akeady discovered at i;\-oolhope, but also typical fossils, 

 which might be found there, from the district of SUuria proper. 



Our thanks must be given to those gentlemen who lent the specimens, 

 from which the present illustrations are diawn, bravely disregarding the danger 

 of scientific kleptomania. W^e would also give notice that any members of the 

 Club, or others, possessing remarkable Upper Silurian Lamellibranchiata, 

 Brachiopoda or Bryozoa, especiaUy if found at Woolhope, are requested to 

 communicate with the Secretary or the Central Committee during the ensuing 

 summer. 



SUB-KINGDOM MOLLUSCA. 

 This great primary division of the animal kingdom is composed of soft 

 invertebrate organisms, having a gangliated nervous system, and characterised 

 in general by an entire want of symmetry : in the highest class only do we find 

 anything that corresponds to the internal skeleton of the Vertebrata. Their 

 bodies, however, are often protected by an appendage called a shell, formed by 

 secretion of a combination of earthy and animal matter ; and it is to the durabiUty 

 of the former, consisting as it does chiefly of carbonate of lime, that we owe the 

 preservation in the oldest sedimentary rocks of remains of these animals. To the 

 geologist they are especially important, affording, when lithological and other 

 chara°cters are doubtful, the most complete evidence for the identification of 

 strata. In minuter classification, however, the sheU is of secondary importance' 

 Conchology having been found, like the Linnajan System of Botany, to bring 

 together species of essentiaUy different characters. Inasmuch, th^n, as the 

 softness of body prevents the recognition of its form and structure after death, 

 there wUl alw^iys necessarily be great difficulty in correctly ranging the fossil 

 remains of this animal sub-kingdom. 



The following is the classification most commonly adopted, formed upon 

 certain peculiarities of the organs of motion, position of gills or other characters, 



