are the work of the author alone, and, with the exception of a 

 few of the larger habit sketches, all drawings have been first 

 traced by means of the camera lucida, thus insuring a reason- 

 able degree of accuracy in the relative position, shape, and 

 size of the various structures figured. The drawings of most 

 of the dissections have been made from permanent glycerine- 

 jelly mica-covered slides which are to be found in the Her- 

 barium in the proper pocket with the specimen. 



Special acknowledgement should be here made to Dr. W. 

 J. Holland, Director of the Carnegie Museum, without whose 

 generous and kindly support the collections could not have 

 been made and properly studied nor the Manual prepared. To 

 Professor J. C. Fettermann, of the University of Pittsburgh, 

 is due many thanks for suggestions and criticism, and to Mrs. 

 O. E. Jennings is due much credit for assistance in the collec- 

 tion of specimens, in the preparation of the manuscript, and 

 in the arrangement of the figures on the plates. 



Otto E. Jennings, 



Carnegie Museum, September, 1912. 



