PLATE XVI. 



PAGE 



Fig. 1. Aviotjlopeoten bublingtonensis, M. and W 231 



1 a. View of left valve, with surface partly exfoliated. 

 16. A portion of the surface, magnified. 



Fig. 2. Zeaobinus Tboostanus, M. and W 186 



Body and arms entire. 



Fig. 3. Pal^ohinits buelingtonensis, M. and W 230 



3 a. View of a specimen, showing a part of the ambulacral and inter-ambula- 

 cral plates. 



3 b. An enlarged view of a part of one of the ambulacra, and the adjacent 

 inter-ambulacral plates on each side. 



3 c. One of the surface spines, magnified about three diameters. 



Fig. 4. PoTEBiooEiNus Swalloyi, M. and W 183 



4 a. View of anterior side of body and arms. 



4 b. View of posterior side same. 



Fig. 5. DioHOCEmus oonus, M. and W 169 



5 a. Side view of a specimen without arms. 



5 b. Posterior view of same. 



Fig. 6. Stbotoobixus eegalis 192 



6 a. Anterior view of the bod}-, with expanded vault and arms broken away. 

 6 b. Posterior view of same . 



