PLATE 26. 



* 



r\a. 1. 470. ]. Pknt/\mkrt:s oblongus. ( Pag. 79.) 



1 o. b. A cast ; views of the dui'sal and ventral valves of a very large and gibbons specimen. 

 1 c. Cardinal view of the same, showing casts of tlie interlaminar spaces. 

 1 d. Profile view of lli" same, showing strong concentric riflgcs of growtli. 



