OF THE UNITED STATES. 79 



base, and having, in addition, from sixteen to twenty lines run- 

 ning from the apex to the base. 



Found with the preceding species. 



The ambulacra of these two fossils extend to the mouth, 

 or they would have belonged to the genus Spatangus, 

 with which I think they should be associated, notwith- 

 standing. 



POLYPI. 



Flustra, Lam. 



F. sagena, (S. G. M.) PL xiii, fig, 7. 



Compare with Ellis, Nat. Hist. Cor. pi. xxix, fig. a. 



Abundant in the calcareous strata of New Jersey, where 



it occurs in thin expanded laminae, an inch or two inches 



in diameter. Perhaps this is an Eschara. 



Eschara, Lam. 



E. digitata, (S. G. M.) PL xiii, fig. 8. 



Specific character 



Strongly resembles E. dichotoma, Goldf., from Maes- 

 tricht, (Petrifacten, tab. viii, fig. 15.) 

 Common in the calcareous strata. 



Retepora. 



Found with the preceding genera, but is rare. It is 

 well represented by a species from Maestricht, delineated 

 by Faujas (Hist. Nat. pi. xxxix, fig. 2,) who calls it a 

 Gorgonia. Dr. Goldfuss figures a specimen also from 



