12 



" For the above reasons, I think it will constitute a new ge- 

 nus, peculiar to the Lower Palaeozoic rocks. The horizontal 

 section seems to present an internal arrangement of cells sim- 

 ilar to those of Orbitoides." 



Under this genus is described as follows, page 587 : 



" Selenoides Iowensis, ?1. II B, fig. 13. 



" Specific Character. — One side flatly dome shaped, the 

 other ring shaped, enclosing an umbilicus or central depres- 

 sion. Small rhomboidal cells opening on the surface in curved 

 rows, intersecting in arches ; the cells gradually increasing in 

 size from the inner margin to the periphery." 



Having examined specimens of this fossil from the same 

 locality as that figured by Dr. Owen, I am constrained to be- 

 lieve that this also is a species of Receptaculites of different 

 form from the prevailing one, and varying little if at all specif- 

 ically from that figured under the name of Orbitolites reticulata, 

 in 1844, before referred to. 



In Palaeontology of New York, 1847, Vol.1, p. — , I described 

 a species of Receptaculites, referring it with doubt to the 

 R. Neptuni of De France. The specimen is solid, partly 

 weathered on one side, and furnishes only unsatisfactory 

 means of comparison and determination. More recently, Mr. 

 Salter has stiidied a collection of specimens from Canada, 

 which he regards as identical with the one figured by me, but 

 differing from the European R. Neptuni, and proposes the 

 name R. occidentatis for the Ameriman species.* In the vol- 

 ume referred to I also noticed and figured a fossil of discoid 

 form with depressed centre ; the weathered surface showing a 

 reticulate texture ; but the interior so entirely solid as to re- 

 veal no structure ; and it could not be satisfactorily referred 

 to any known genus at that time. Since knowing the western 

 forms, I have become satisfied that this is generically and per- 

 haps specifically identical with the fossil described fcy Dr. 

 Owen as Selenoides Iowensis, which, when the surface is entire, 

 has a similar reticulated structure. Its diameter is greater 

 than any of the western specimens ; but its condition does not 

 admit of structural comparison. 



In the study of the specimens collected in the lead region, 

 I recognize four principal and prevailing forms of this genus ; 

 the most common and largest of which is the one originally 

 referred to Ooscinopora sulcata. 



<& iguroa and descriptions o' Canadian Organic Remains. Decade I, page 47-49, pi. 10. 



