374 



Dr. J. J. Bigsby's Brief Account of the 



[Feb. 21, 



Until some sucli record as the present is available, the labours of many- 

 living investigators (whose names rise to the lips spontaneously) will rest 

 comparatively fruitless. It has hitherto not been possible to consider 

 widely scattered existences in an aggregate form. Facts (many) have been 

 stored up separately ; but generalized truths have been rarely attained. 

 This has not yet been done in a satisfactory manner, not even by Bronn or 

 Goldfuss for any one epoch, and scarcely for the cretaceous period by the 

 American geologist Mr. Gabb, although he has done well. 



This 'Thesaurus' contains 7553 species, and therefore gives abundant 

 scope for profitable study ; but probably it does not give the tithe of the 

 •whole Silurian life yet lying buried in the wilds of the Arctic Circle, of 

 Hudson's Bay, Labrador, the two Americas, Scandinavia, Australia, India, 

 &c. &c. The more accessible countries frequently, to this day, yield new 

 forms, although the search for them is capriciously and idly conducted, 

 and is dependent often on the accident of a new^ public work or the pre- 

 sence of a competent observer. Many undescribed species are lying in 

 local museums, still more in the great collection at Prague in the posses- 

 sion of a high Ecclesiastic in that city. Owing to the enhghtened perse- 

 verance of M. Barrande, a few small parishes close to Prague have yielded 

 nearly one-third of the whole earth's Silurian remains within present 

 knowledge; and the greater part of these are not met with elsewhere. 

 How wonderfully rich must be the universal Silurian fauna! What a 

 splendid promise to the future explorer ! 



The ' Thesaurus ' is in the form of a Table. After mentioning the genus 

 (taken alphabetically), its author, and the date of its estabhshment, the 

 species are successively named, and treated of under four or more heads, 

 along one and the same ruled line. First comes the part of the stage in 

 ■which it occurs, then, in a given order, its author and locality, or localities, 

 in the column indicative of its proper stage. 



More information is thus conveyed, it is believed, than by any other 

 form of Table. The summaiy which is appended to each order shows some 

 of the organic relations of the Silurian system in Europe and in America 

 to each other ; it shows, too, how very little w^e know as yet of this epoch in 

 Asia and Africa ; and, among other things, it tells us the numerical strength 

 of the genera. 



Permit me now to lay before the Society a few facts drawn from the 

 mere surface of the ' Thesaurus,' and only in the way of summary or brief 

 remark, in order to suit the purpose of this evening. Much more than 

 this the careful registration of more than 50,000 facts has prevented me 

 from doing. 



The Table A (page 375) gives the numerical amount of the Silurian flora 

 and fauna as known in the years 1856 and 1866 respectively. 



