INTRODUCTION. VU 



have changed hands, and fresh causes of error have crept in. The 

 present condition of the Cumingian Collection has been faithfully 

 described by Dr. Gray in the Proceedings of the Zoological So- 

 ciety ; and those who will take the trouble to compare his review 

 of the Calyptraeidas, after the destruction of original labels conse- 

 quent on Reeve's Monograph, with that which I gave in the 

 Mazatlan Catalogue, while these labels were still fixed to the 

 shells, will appreciate the advantages which I formerly enjoyed. 



Readers who may discover any uncorrected errors in this 

 volume, or in any of my other works, are urgently requested 

 to apprise me of them (Box 193^ P. 0., Montreal, C. E.), in 

 order that they may be corrected in the Report of the Mollusca 

 which Prof. Whitney has requested me to prepare for the Cali- 

 fornia Geological Survey. 



PHILIP P. CARPENTER. 



Montreal, July 17, 1872. 



