34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



DESCRIPTION OF PLATE 4 



PAGE 



Sidneyia inexpectans Walcott 24 



Fig. I. Outer portion of the third pair of appendages of the cephalo- 

 thorax (X2). In this there appears to have been a some- 

 what different development of parts as compared with those 

 seen in figs. 3 and 4. U. S. National Museum, Catalogue 

 No. 57490. 



2. Another form of the outward extension of one of the third pair 



of appendages of the cephalo-thorax (X2). This type 

 reaches a very large- size ; one has a length of 65 mm. U. S. 

 National Museum, Catalogue No. 57491. 



3. Outer extension of a part of one of the outer portions of the 



compound chelate termination of a third appendage (X2). 

 The anterior arm, as shown in figs, i and 4, is broken away. 

 U. S. National Museum, Catalogue No. 57492. 



4. Outer portion of one of the third pair of appendages of the 



cephalo-thorax, showing on the jointed primary appendage 

 large, elongated spines with spinose fringes and a short, 

 jointed appendage attached to the posterior outer side of 

 the gnathobase. X 2. U. S. National Museum, Catalogue 

 No. 57493- 



