FOREWORD. 7 



When the writer, in the autumn of 1904, succeeded Professor Beecher in the chair of 

 Pakeontology at Yale, he expected to find considerable manuscript relating to the ventral 

 anatomy of the trilobites, but there was only one page. It was Beecher's method first to 

 prepare and thoroughly study the material in hand, then to make the necessary illustrations, 

 and between times to read what others had written. There was no written output until 

 everything had been investigated and read, certain passages being marked for later reference. 

 Then when all was assimilated, he would write the headings of topics as they came to him, 

 later cutting them apart and arranging them in a logical sequence. When the writer visited 

 him in his home in January 1904, he was primed for his final trilobite memoir, but the 

 writing of it had not been begun. 



The writer has never made the trilobites his special subjects for study as he has the 

 brachiopods, and therefore felt that he should not try to bring to light merely the material 

 things that Beecher had so well wrought out. It seemed at first an impossible task to 

 find the specialist and friend to do Beecher justice, but as the years have passed, one of 

 Beecher's students, always especially interested in trilobites, has grown into a full appre- 

 ciation of their structures and significance, and to him has fallen the continuation of his 

 master's work. If in the following pages he departs here and there from the accepted inter- 

 pretation and the results of others, it is because his scientific training, in desiring to see with 

 his own eyes the structures as they are, has led him to accept only those interpretations 

 that are based on tangible evidence as he understands such. Furthermore, in seeking the 

 relationship of the trilobites to the rest of the Arthropoda, his wide study of material and 

 literature, checked up by the ontogeny of fossil and recent forms, has led him in places from 

 the beaten path of supposedly ascertained phylogenies. His results, however, have been won 

 through a detailed study of the interrelations of the Arthropoda, starting from the fact 

 that the Trilobita are chronogenetically the oldest and most primitive. The trilobites are 

 held by him to be the most simple, generalized, ancient Crustacea known, and the progen- 

 itors,'- directly and indirectly, of all Arthropoda. 



It is now twenty-six years since Professor Beecher began his publications on the class 

 Trilobita, and in commemoration of him and his work, Professor Percy E. Raymond of Har- 

 vard University presents this memoir, to bring to fruition the studies and teachings of his 

 honored guide. It has been with Professor Raymond a labor of love, and it is for the 

 writer of this foreword a long-desired memorial to the man to whose position in the Museum 

 and University he had the privilege of succeeding. 



Yale University, New Haven, Connecticut. 



