30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



DESCRIPTION OF PLATE 2 



PAGE 



Sidneyia inexpectans Walcott 24 



Fig. I. A large dorsal shield (natural size) flattened and somewhat 

 broken by compression in the shale; an antenna projects out 

 from each side in front of the eye, and, on the right-hand 

 side, probably the fourth appendage of the cephalo-thorax 

 which has been pushed back under the second segment of the 

 abdomen. U. S. National Museum, Catalogue No. 57487- 



2. Enlargement of the under side of a small cephalo-thorax to 



which are attached the antennae and four pairs of ap- 

 pendages. Only a portion of the epistoma is preserved. This 

 is the only specimen in the collection preserving the ap- 

 pendages of the cephalo-thorax in their approximately nor- 

 mal position. X 3- U. S. National Museum, Catalogue No. 

 57488. 



3. A portion of the matrix of the specimen represented by fig. i. 



X3. 



The illustration on pis. 2-7 are from photographs taken by 

 Mr. J. M. Jessup and slightly retouched by pencil. 



