BIOGRAPHICAL SKF.TCTT OF ISAAC LEA, LL. D. XXI 



of papers on the subject, also occasionally a paper ou a geological sub- 

 ject, as a reference to bis bibliograi)hy will show. Some of these were 

 eminently important, particularly the continuation of his papers on new 

 Unionidcv, their anatomy and physiology, and the one on the foot prints 

 of the t^nuropus primccvus found by him in the Eed Shales at Pottsville, 

 Pa., 1,700 feet below the conglomerate, being in Professor Rogers's For- 

 mation iSTo. XI, and which constitutes the oldest case of an air-breathing 

 animal on record. 



Professor Agassiz, however, at the meeting of. the American Asso- 

 ciation of Science at Kew Haven, asserted that he "did not believe 

 that any air-breathing aninials had existed before the New Red Sand- 

 stone." 



This assertion was made notwithstanding Dr. King had published 

 his discovery of saurian foot-prints near Greensburg, Pa., between the 

 coal strata in Rogers's Formation ]S"o. XIII. These foot-prints are several 

 thousand feet above those mentioned by Mr. Lea in Xo. XL 



Professor Rogers subsequently^ procured through Professor Sheafer, 

 the geologist, and his assistant, impressions of the same species at the 

 same locality. Mr. Lea was well aware of the great importance of tliis 

 discovery, and some years after his publication in the "Transactions of 

 the American Philosophical Society," with reduced figures on stone, he 

 issued a fine edition in large elephant folio, which enabled him to print 

 the figures life-size in the exact color of the Red Shale, thus producing 

 a fac-simile of the original. The type was necessarily so large that he 

 had to have it cast for the purpose, and the paper was also made ex- 

 pressly for the work. The whole Was eminently successful, and it pre- 

 sents a specimen worthy of American typography and book-making 

 which is nowhere excelled. 



Previous to this he published numerous papers on fluviatile and 

 terrestrial mollusca, and his important paper on the description of the 

 " Clepsysaurus Pennsylvanicus, of the ISJew Red Sandstone Formation 

 of Pennsylvania." 



Having retired from business, he determined to revisit Europe, and 

 took passage from Philadelphia, in the steamer City of Manchester, 

 June 3, 1852, accompanied by his wife, daughter, and sister. 



Arriving at Liverpool on the 17th of June, he spent four or five days 

 with his old friend and correspondent, William Rath bone, esq., and was 

 very glad to see again his friend Prof Thomas Xuttall,* who was in- 

 vited with several others to meet Mr. Lea at dinner. 



* Professor Nuttall, the eminent botanist and ornithologist, had returned to Eng- 

 land to reside, a fortune having been left him by an uncle on condition that he 

 should not leave England more than three months of each year. This was hard for 

 such a thorough lover of nature as Professor Nuttall to assent to and was accepted 

 only for the sake of his two sisters. He nevertheless managed to have six months by 

 taking the last of one year and the beginning of another. This was his method, as 

 he told Mr. Lea at his house in Philadelphia, where the professor was a frequent and 

 always a welcome guest. 



