

THE 





AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.! 



Art. XXIX. — The Morphology of Triarthrus ; by C. E. 

 Beechee. (With Plate VIII.) 



Most of the recent advances in the knowledge of trilobite 

 structure have come from the study of Triarthrus. Since 

 Valiant's discovery of the antennse, and its announcement by 

 Matthew in 1893, the writer has published a series of papers 

 on the detailed structure of this trilobite. Much time has 

 also been spent in carefully working out the numerous speci- 

 mens from the abundant material in the Yale Museum. Alto- 

 gether upwards of five hundred individuals with appendages 

 more or less complete have been investigated ; and at the 

 present time, it may safely be said that the important exoskel- 

 etal features have been seen and described.* 



Notwithstanding the amount of information regarding the 

 details of the various organs, very little has been shown illus- 

 trating the general appearance of the animal with the append- 

 ages in a natural and lifelike position, and it is one object of 

 the present article to supply this deficiency. 



Several specimens have been lately developed which pre- 

 serve not only the appendages in great perfection, but also 

 show them extended and disposed in a very lifelike manner. 

 No new structural points are here brought out, yet the repre- 

 sentation of the complete animal serves as a summary of 

 present knowledge, and also gives a definite picture of great 

 assistance in forming a conception of general trilobite mor- 

 phology. 



* The more important literature relating to the structure of the genus Triarthrus 

 is given at the end of the present article ; numbers in the text refer to this. 



Am. Jour. Sci. — Fourth Series, Yol. I, No. 4. — April, 1896. 

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