1908.] NATURAL SCIENCES OF PHILADELPHIA. 515 



revision of any group, those who have contributed most to the subject 

 should bring their collections together in one place, and there they 

 should institute their comparisons conjointly. I stated in my memoir of 

 1904: "This paper is by no means a comprehensive monograph, but 

 is intended to be a help to the one who comes later with sufficient 

 material at his disposal to make the monograph." The main defi- 

 ciency in Prof. Chamberlin's revision seems to have been insufficient 

 type material. 



