116 Sellards — Structure of Paleozoic Cockroaches, 



visits to the locality resulted in the discovery of as many as 

 fifty specimens, indicating the comparative abundance of the 

 insects. Later in the summer the Kansas Geological Survey 

 sent a party into the Held and obtained in all over two hundred 

 specimens, among them a considerable number of immature 

 forms, or nymphs, or more properly in most cases the shed- 

 dings or moults of nymphs. In the fall of the same year, 

 Professor C. E. Beecher very generously placed at the writer's 

 disposal for study the Yale collection of paleozoic cockroaches, 

 especially rich both in nymphs and in adults preserving structural 

 characters. During the past two summers the writer has 

 almost doubled the original number of specimens from the 

 Lawrence Shales, the later collections containing especially 

 instructive nymphs. More recently, Mr. Charles Schuchert has 

 very kindly sent for comparison and study the cockroaches 

 from Mazon Creek contained in the Lacoe collection of the 

 United States National Museum. Mr. L. E. Daniels, through 

 Mr. Schuchert, has loaned from his private collection several 

 specimens from the Mazon Creek locality. During the sum- 

 mers of 1902 and 1903 the writer also obtained a collection of 

 over two thousand fossil insects from a new locality in the 

 Permian of Kansas. Cockroaches in the Kansas Permian are 

 very much in the minority as compared with other families. 

 A considerable number, however, were secured, and these, 

 although not described in detail, have been useful in compar- 

 ing with those from lower horizons. 



Acknowledgments. — The results of an investigation of this 

 kind depend to a considerable extent upon the success of devel- 

 oping and cleaning the fossils. This is especially true of the 

 Mazon Creek specimens, in which the contrast between fossil 

 and matrix is often slight, and the indurated nodules are diffi- 

 cult to work. It was the writer's good fortune in this study to 

 have the advantage of the direction and guidance of the late 

 Professor C. E. Beecher, whose skill in preparing and wide 

 experience with fossils made his suggestions of inestimable 

 value. Moreover, not a little of the skill and ingenuity for 

 which this master of paleontological technique was famous had 

 been expended, with the usual excellent results, ou several of 

 the Mazon Creek specimens of the Yale Museum before the 

 collection came into the writer's hands for study. It is also a 

 pleasure to acknowledge indebtedness to Dr. S. W. Williston, 

 Mr. Charles Schuchert and Mr. L. E. Daniels. Dr. Williston' 

 encouraged the development of the Lawrence locality, and 

 made the collections belonging to the University of Kansas 

 accessible for study. Mr. Schuchert has contributed not a 



