Fossils of the Hamilton Group. 



475 



Generic name from the Greek a, without, and trupa, a perfora- 

 tion; prisca^ old, ancient. 



Fig. 12. Orthonota undulata. 



Fig. 12. Orthonota undulata. Professor Hall says this fossil is 

 more common in the eastern part of the State of New York than 

 in the western. It may yet be found in Canada, and therefore we 

 publish it here. 



OrtJionota^ from the Greek orthos^ straight, and notatus, marked. 



Fig. 12. Ci/pricardia recurva. 



Fig. 12. Cypricardia recurva is given by Mr. Vanuxem, as 

 being a common fossil of this group of rocks. It is remarkable 

 for its curved form : hence the specific name. 



Fig. 13. Avicula Jiahella. 



