CHAPTER VXI. 



NEW AND LITTLE KNOWN LAMELLIBRANCHIATA FROM 



THE LOWER SILURIAN ROCKS OF OHIO AND 



ADJACENT STATES. 



By E. O. Ulrich. 



Description and figures of many of the following species were pre- 

 pared in 1881 for Dr. Newberry's proposed Volume III on the Paleontol- 

 ogy of Ohio. After successive failures to secure an appropriation from 

 the legislature, the plan of publication by the Ohio Survey seems to have 

 been abandoned, since much of the work prepared for the volume has 

 appeared through other channels. The same course would have been 

 adopted in my own case had my plates not been destroyed in a fire at the 

 lithographing establishment that was to print them. 



Although at the time a great disappointment, I cannot but believe 

 that science has, after all, gained through their loss, for the work as now 

 presented is more thorough and as I believe better in every respect. 

 Whether it is accepted as good or not, the fact will remain that I have 

 spent a great deal of time and labor on the class and that I have conscien- 

 tiously striven to do my best under what, to say the least, were not 

 always favorable circumstances. 



The present addition to our knowledge of paleozoic Lamellibranehi- 

 ata is really to be viewed as supplemental to the work which I have just 

 completed for the paleontological report of the Minnesota Geological 

 Survey. In that work, which is now going through the press, the stu- 

 dent will find an amended classification of the paleozoic representatives 

 of the class and full descriptions of nearly all the genera occurring in the 

 Lower Silurian rocks of America. It may have seemed to those who 

 were not conversant with the facts that much had been done on the 

 Lower Silurian forms previous to the present decade, but I would assure 

 them that it amounts to little indeed compared with what has been done 

 since the beginning of 1890 and what remains yet to be accomplished. 

 Including the present work no less than twenty-three new genera have 

 been proposed by the author, and four by Mr. S. A. Miller for Lower 

 Silurian types.. 



The erection of a new genus is a serious matter and, unless the 

 type is very obviously distinct, ought not to be attempted except on suf- 

 ficient evidence showing that the proposed grouping of species actually 



