478 PALEONTOLOGY OF ILLINOIS. 



from a crushed specimen of Oligoporus Dance, that the species of this 

 group have the jaws very like those of Melon-ties. The question may 

 therefore arise whether or not these differences in the number of pieces 

 and pores of the ambulacra are of generic importance, and whether we 

 ought not to regard them as only subgeneric, and call our species Mel- 

 onites f Oligoporus j nobilis. On the same grounds, however, we would 

 have as good reason to regard both Oligoporus and Melonites as mere 

 sections or subgeuera of Palcechinus. We cannot, however, believe so 

 important and constant a difference of less than generic value, no gra- 

 dations being yet known in this character between Oligoporus and Mel- 

 onites on the one hand, or between the former and Palcecliinus on the 

 other. It is true, we yet only know 7 one species of Melonites, but we 

 now know two well marked species of Oligoporus, while there are eight 

 or nine known distinct species of Palwcliinus, all of which latter agree 

 in having but two rows of ambulacral pieces to each area. 



At the time we proposed the name Oligoporus we were not aware that 

 Prof. DESOR had designated a section (not a genus) of the family C-ida- 

 ridce by the name Oligopores. In case this should be regarded as a 

 serious objection to our name Oligoporus we suggested, in the second 

 volume of the Illinois Geological Reports, the name Melonopsis for this 

 group instead ; and if it should be adopted, the species here described 

 would have to be called Melonopsis nobilis. The name Oligopores, how- 

 ever, from its different termination, we should think sufficiently dis- 

 tinct. 



Locality and position Calhoun county, Illinois ; from the Burlington 

 division of the Lower Carboniferous series.' 



GENUS EOCIDAKIS. 

 EociDARisI SQUAMOSUS, M. and W. 



PI. 9, Fig. 15. 

 Eoddaris? squamosus, MEEK and WORTHEN. Proceed. Acad. Nat. Sci., Phila., 1869, p. 79. 



BODY attaining a large size, apparently depressed sub- 

 globose in general form. Iiiterambulacral plates rather 

 thick, in eight or more longitudinal rows near the middle 

 of each area,* but apparently only the two outer rows con- 

 tinued to the oral apertures, all presenting the usual hex- 

 agonal form, excepting the pentagonal marginal rows, and 



* Eight rows are seen in the specimen at the widest part, but we are not sure this is the middle of 

 the area, owing to the imperfection of the specimen. 



