BIOGRAPHICAL SKETCH OF ISAAC LEA, LL. D LV 



Paris, Fchruary 11, 1860. 

 My Dear Sir : A thousand thanks for the iiarcel which yon have had the goodness 

 to send me, consisting of the second part of volume 6 of your observations on the genua 

 Unio, and the pamphlet which accompanied it. 



Your work upon the Unio is certainly the most beautiful and complete which we 

 have upon this magnificent genus, aud I might say the only one, for I do not count 

 as anything the article which M. Chenu has given in his " Conchological Illustra- 

 tions," where he has copied your figures, and has also depended on you for the text. 

 You render a great service to science in devoting your time to the classification and 

 description of the Unio. I trust that Heaven will give you a long life, both for your 

 sake and our own. 



With the warmest expression of my attachment, I am, yours, most sincerely, 



A. BOIVIN. 



Dr. Lea's cabinet of Vnionidce consists of horizontal cases in two large 

 rooms, in which cases there are displayed to view about ten thousand 

 individuals, of different ages, so arranged that each may be separately 

 examined. In fact, this collection is unique in having many species 

 arranged with a sequence from the youngest to the oldest, so that the 

 student may see at a glance the aspect of their growtb. 



Thus a suite of dififererent ages may consist of a dozen or more, no 

 two being exactly the same. 



Where the female differs in outline from the male there is also a suite 

 of ages which generally marks the age of puberty. A suite of aberrant 

 forms is also given, so that there may be fifty specimens of a single 

 species, there being no two exactly the same. The whole of this col- 

 lection is arranged on grooved wooden slats, with the left valve under- 

 neath, the anterior part to the right, aud the beaks uppermost, thus 

 giving a comparative view of the outline of one species with another. 

 He began this collection in 1825, and has continued adding to it un- 

 remittingly to the present time. It is so complete that if all the col- 

 lections known were selected from, one similar to it could not be made. 

 The collection of fresh-water univalves is also large, consisting of sev- 

 eral thousand. The collection of fossils is classified and placed in 

 stratifications from the Archaic to the Tertiary formations. His collec- 

 tion of land shells is also very extensive, consisting of many rare species 

 from almost every part of the globe, and that of marine mollusca is 

 large aud complete, containing, as it does, many rare genera aud spe- 

 cies. 



Dr. Lea's first memoir of that remarkable series on the Unionidce, &c., 

 was published in the Transactions of the American Philosophical So- 

 ciety in 1827, vol. 3, new series, and were continued in vols. 4, 5, 6, 

 and 7. Subsequently he published them in the Journal of the Acad- 

 emy of Natural Sciences until 1876, when they were discontinued (ow- 

 ing to illness). He had printed for his own use two hundred and fifty 

 copies, forming thirteen volumes, with three indices. These were gra- 

 tuitously distributed to scientists and to learned societies. 



Dr. Lea has preserved all his scientific correspondence since 1818, 

 and these numerous letters show the development of fresh water and 



