EXPLANATION OF PLATE XL 



Fig. 1. AvicuLOi'ECTEN Corkvanus. (Pago 147.) 



a. Left valve, a natural cast ; tlie test nautiug. 



I). Left valve of similar character, somewhat distorted by iiressure. 

 Fig. 2. AvicuLOPECTEN' M'CoYi. (Pago 149.) 



a. Left valve. The e.xamplo is inconipleto, but the full size of the ears is either shown or 

 indicated. The free border should be extended about one-third more for ears of that 

 size. 

 Fig. 3. Aviculoi'ecten ? ixteulineatus. (Page 149.) 



a. Left valve. 

 Fig. 4. MoxoPTEiuA MAniAX. (Page 151.) 



a. Eight valve. t5ome examples show a little greater proportionate elongation, and some have 

 the median angle raised into a distinct carina. 



h. Front view, showing lunule. 



c. Fragment of surface enlarged, showing striaj of growth. 

 FiG. 5. PiNN'A I'ERACUTA? (Page 151.) 



a. Fragment of the right valve. The outline shows the supposed shape of the whole valve 



Fig. G. Sciiizodus Wheeleki. (Page 154.) 



a. Right valve, of about ordinary size. Natural cast ; the test wanting. 



h. Left valve, in a similar condition. 

 Fig. 7. Bakevellia paiiva. (Page 153.) 



a. Left valve, enlarged. From New Mexico. 



b. Left valve, enlarged. From Arizona. Probably of the same species as the other. 

 Fig. 8. Myali.va? Swallovi. (Page 152.) 



a. Natural cast of left valve, natural size. 

 Fig. 9. Spiiiifer Eockv.montanus. (Page 134.) 



a. Ventral view of a specimen of ordinary size. 

 6. Dorsal view of the same. 



c. Lateral view of the same. 



il. Dorsal view of another example, having iilications a little more angular. 

 Fig. 10. Tep.ebratula (Diklasma) bovidens. (Page 144.) 



a. Ventral view of more than usually elongate example. 



b. Dorsal view of the same. 



c. Lateral view of the same. 



