NEW SPECIES OF TRILOBITE. 



223 



county, Ohio, in 183S. It was about six inches of the marginal 

 " cavetto " of the tail, beautifully veined, marlced with the tuber- 

 cle, perfectly elliptical, and coinciding mth the end of an ellipse 

 twenty-two inches long and twelve inches broad. The second 

 specimen was an entire tail found at the same locality ; this, upon 

 admeasurement, was found to coincide with an ellipse of exactly 

 half of the dimensions of that which suited the first specimen, 

 and showed, by a fortunate fracture, the internal marginal cavetto. 

 These two specimens were both figured and described by me in 

 the Ohio Geological Report for 1839. 



The third specimen (see outline) was discovered in the autumn 

 of the same year by Wra. Burnett, Esq., on the hills at Cincinnati, 

 and presented to me soon after. It was partly covered by the 

 crystalUne blue limestone in which it had been imbedded, and it 

 was not until the winter of 1840-41 that I dissected it out of its 

 gangue, and found that it had an aculeate shield, and that it ex- 

 hibited the animal almost entire. 



It is of the same dimensions as the second specimen, and 

 measm-es nine inches and three fourths in length, and six inches 

 in breadth. The first fragment must therefore have been from a 

 specimen nineteen inches and a half long, and twelve inches 

 broad. These gigantic dimensions suggested the name niaxi- 

 mus, which I gave in the Ohio Report, but which, for obvious 

 reasons, I have changed to the more classical Greek term of the 

 same import. 



The fourth specimen was discovered by Mr. Carley, of Cin- 

 cinnati, w^ho was the first to discover the aculeate shield, for in 

 the Burnett specimen this character was still concealed. IMr. 

 Carley's specimen appears to be a young one, for it is only about 

 three inches long. It was obtained in the bed of the Ohio river 

 about four or five hundred feet lower than the situation which 

 furnished the Burnett specimen. My own first specimens were 

 found within thirty feet of the top of the blue limestone forma- 

 tion, where it is overlaid by the clifi" limestone. Now the char- 

 acter of this magnificent species of trilobite has been ascertained, 

 it is evident that fragments of it are abundant in our blue lime- 

 stone, which is undoubtedly the equivalent of the limestone of 



