iv PREFACE. 



the National Museum, and to Mr. Richard Rathbun, Curator of Invertebrata. 

 Of the types of Girard's and Stimpson's species which this collection once 

 contained, I was able to find only two, C. Pcalei Gir. (= C. affinis Say) and 

 A. Trowlridgii Stra. The rest were probably lost in the great fire of Chi- 

 cago in 1871, while in Stimpson's hands. 



2. Through the courtesy of the Council of the Academy of Natural 

 Sciences of Philadelphia, I have had the opportunity to inspect the Asta- 

 cidjB in the collection belonging to the Academy ; and the specimens that 

 demanded more than a cursory examination have been sent to me in Cam- 

 bridge. This collection, although small, is of great historical interest, since 

 it contains many apparently authoritative examples of Girard's species, to- 

 gether with types of species described by Harlan, Gibbes, and Le Conte. 

 It was examined by Hagen also in the course of the preparation of his 

 Monograph. 



3. The collection of the Peabody Museum of Yale College, New Haven, 

 Conn., containing types of Astacus Troivlridgii Stimpson and Oambarus Sloanii 

 Bundy. 



4. The Astacidte belonging to the Boston Society of Natural History. 



5. The collection of the Peabody Academy of Science, Salem, Mass. 



6. The valuable collection of Maryland and Virginia Cambari brought 

 together by Mr. P. R. Uhler, of Baltimore, Maryland. This collection is con- 

 tained in upward of one hundred and eighty jars. Through the labors of 

 Mr. Uhler, Maryland is now one of the best explored States in the Union. 



7. Prof. 0. P. Hay of Butler University, Irvington, Indiana, has kindly 

 offered for my examination an interesting collection of sixteen species of 

 Cambarus secured in the West and South by himself and Prof. D. S. Jordan. 



I take this opportunity also to acknowledge the loan of specimens from 

 the private collections of Professors L. A. Lee, R. R. Wright, A. S. Packard, 

 D. S. Jordan, and B. F. Koons, Dr. C. H. Merriam, and Messrs. R. S. Tarr 

 and C. II. Gilbert. 



The second part of this Revision will include the crayfishes of the South- 

 ern hemisphere, the Parastacinse. 



