VI PREFACE. 



particular species may not be found is of no import- 

 ance, as the end in view is not to provide a monograph 

 on any one species, but to show a student " How to dis- 

 sect a Chelonian." The members of the order are so 

 similar in all important points that the best method of 

 examining the structure of one species is the best also 

 for almost any other. I am not sure, in fact, that it is 

 not better in all cases to provide students with species 

 slightly different from the one described ; their atten- 

 tion is kept more alert when they find they cannot alto- 

 gether rely on the description in the book, but have to 

 look at everything carefully for themselves. 



These directions for dissection are of course not 

 meant to be used by themselves, but to accompany 

 lectures on the class and order of the type described, or 

 the reading of a good text-book. Some knowledge of 

 human osteology, which affords the best starting-point 

 for every student of vertebrate morphology, is also 

 assumed. 



H. NEWELL MARTIN. 

 Baltimore, July i, 1881. 



