4. ON THE MODE OF OCCURRENCE AND THE 



STRUCTURE AND DEVELOPMENT OP 



TEIARTHRUS BECKI* 



(Plate VI) 



The presence of antennae and other appendages on a trilo- 

 bite from the Utica Slate was announced in May, 1893, 

 by W. D. Matthew. t The specimens were discovered by 

 W. S. Valiant, J near Rome, New York, where they occur 

 in a fine-grained carbonaceous shale. It was apparent that 

 specimens preserving organs so delicate as antennae ought to 

 show, in addition, other anatomical features which would be 

 of great assistance in determining the zoological position of 

 the Trilobita. With this object in view, and with the assist- 

 ance of Professor Marsh, a collection was made for the Yale 

 University Museum. From this material it is hoped that 

 the remaining details in the structure of this important fossil 

 may be made out. The preliminary examination of the speci- 

 mens shows a number of new and remarkable structural 

 features, some of which will be briefly noticed here. It was 

 also possible for the writer to make observations in the field, 

 which furnish interesting facts as to the mode of occurrence 

 and to the habits of the trilobite. 



* Abstract of a paper "On the Structure and Development of Trilobites," 

 read before the National Academy of Sciences, November 8, 1893. American 

 Geologist, XIII, 38-43, pi. iii, 1894. 



t On Antennas and other Appendages of Triarthrus Beckii. Read before 

 the N. Y. Academy of Sciences, May, 1893. Published in Amer. Jour. Sci. (3), 

 XLVI, 121-12.5, August, 1893. 



X Mr. Valiant informs me that he found the first specimen showing antennae 

 in 1884, but it was not until 1892 that other specimens were obtained by him 

 and M. Sid. Mitchell fully establishing the discovery. The specimens sent to 

 Columbia College were collected by W. S. Valiant, of Rutgers College. 



