On American Geological History. 395 



Mr. Conrad remarks that lie " was fortunate enougli to obtain 

 two fine casts of this bivalve, with the teeth remarkably well 

 represented." The figure given by Mr. Conrad, to ilhistrate this 

 fossil, shows the hinge line with a continuous series of eight teeth. 

 The typical species is L. piano. I have referred to this genus a 

 small shell from the Utica slate, which is nearly equilateral, with, 

 equally rounded extremities, and a few distinct teeth on each side 

 of the beak. This shell, L. pulchella^ does not diflfer from TellinO' 

 mya, to which it must be referred. 



The shells of the genus Tellinomya are shown to differ from 

 Nucula, Isoarca, Nuculites, and Cucullella. 



In addition to the species described under this genus in the 

 first volume of the Palaeontology of ISTew York, may be added 

 T. (^Nucula) levata, T. (JVuciila) donaciformis^ T. [lyrodesma) 

 pulchella ; and also the following species, described by Professor 

 Phillips : (Memoirs Geological Survey of Great Britain, vol. 2.) 

 Tellinomya (JVucula) coarctata, T. {Nucula^ deltoidea^ T, 

 {JS'ucula^ lingualis^ T. [JVucula) rhomboidea. 



ARTICLE LVI. — On American Geological History : — Address 

 before the American Association for the Advancement of 

 Science, August, 1855, by James D. Dana.* 



In selecting a topic for this occasion, I have not been without 

 perplexity. Before an Association for the Advancement of 

 Science, — science in its wide range, — a discourse on the progress 

 of science in America for the past year would seem legitimate. 

 Yet it is a fact that the original memoirs in most departments, 

 published within that period, would make a very meagre list. 

 Moreover, it is too much to expect of any one to roam over 

 others territories, lest he ignorantly gather for you noxious weeds. 

 I have, therefore, chosen to confine myself to a single topic, that 

 of Geology ; and I propose, instead of simply reviewing recent 

 geological papers, to restrict myself to some of the general con- 

 clusions that flow from the researches of American geologists, 

 and the bearing of th« facts or conclusions on geological science. 

 I shall touch briefly on the several topics, as it is a subject that 

 would more easily be brought into the compass of six hours than 

 one. In drawing conclusions among conflicting opinions, or on 



* Sillimaa's American Journal of Science, Ifovember, 1856. 



