AMERICAN GEOLOGY DECADE OE 1830-1839. 



305 



Green's Monograph, 

 1832. 



Fig. 21.— Jacob Green. 



The condition of paleontological science at this date (1832), so far as 

 it related to the Trilobites. at least, is shown by Dr. Jacob Green's 

 Monograph of the Trilobites of North America, a duodecimo volume of 

 93 pages and one plate of ten figures. Thirty-three 

 species were described. In a supplement bearing date 

 of 1835 this number was increased to forty. A series 

 of casts, examples of which are still to be 

 found in many of our educational institu- 

 tions, accompanied the original publication. 



The true nature of the TriloMte was at that 

 time not well understood. Green himself 

 seems at first inclined to agree with Latreille, 

 who, owing to their supposed footless con- 

 dition, placed them intermediate between 

 the Chitons and the Articulates." Brong- 

 niart, Dekay, and others, it will be remem- 

 bered, considered them as belonging to the 

 Entomostraca. 



A contemplated chapter on this branch of 

 the subject remained unwritten, since the au- 

 thor felt that all matters of dispute were " put 



to rest by the late discovery of some living trilobites in the southern 

 seas." Concerning the exact position in the zoological scale of these 

 "living" forms there still exists some doubt. Dr. James Eights, who 

 originally described them under the name of Spseroma bwnastiformis, 

 seems to have regarded them as Isopods. Emmons, in his Geology of 

 the Second District of New York, on the other hand, referred to them 

 as Trilobites, while Zittel, in the latest edition of his Handbook on 

 Paleontology, refers them once more to the Isopods. 



Green's ideas as to the value of fossils as indices of geological age 

 were not as advanced as those of most of his colleagues or as his time 

 would lead one to expect. After quoting some of the prevalent opin- 

 ions, he adds in a footnote: 



Nothing can be more opposed to true science than to pronounce on priority of 

 formation or the comparative age of rocks from either their structure or the organic 

 remains they present. 



Concerning Brongniart's expressed opinion relative to the prepon- 

 derating value of fossil over lithological criteria, he wrote: 



This seems to us to imply an admission that nothing definite fan be inferred from 

 the nature of the rocks; moreover, that between the nature of the rock and the organic 

 remains there may be a palpal de discrepancy. * * The event has proved, from 



what we have already mentioned, that no evidence as to priority can be obtained 

 from the nature of the fossil remains displayed in particular strata. 



"The Trilobites have since been shown to have feet. 

 NAT mis 1904 20 



