IOWA ACADEMY OF SCIENCES. 13 



ON THE STRUCTURE AND PROBABLE AFFINITIES OF CERIONITES 

 DACrYLIOIDES OWEN. 



In his ReDort of a Geological Exploration of a part of Iowa, Wisconsin, and 

 Illinois, made under instructions from the Secretary of the Treasury ot the United 

 States in the autumn of the year 1839, Dr. David Dale Owen describes and figures 

 a small fossil from the "Coralline beds of the Upper Masrnesian Cliti Limestone of 

 Iowa and Wisconsin," under the name of Lnnulites? dactioloides. The report was 

 printed in June, 1840, and was reorinted with some additions and emendations in 

 1844. The fossil in question, Luniditcs? dactioloides, is described briefly, as fol- 

 lows, on page 68: Truncated spherical, with five or six sided cellular depressions 

 in rows around the circumference, like those on a thimble, one inch and a quarter 

 in circumference." The illustration of the species. Figure 4, Plate XIII, exhibits 

 a fossil with a spherical surface marked by rounded pits arranged quincuncially. 

 The pits are relatively large and separated from each other by thick walls. Owen's 

 figure is indeed a very imperfect illustration of the fossil as we now know it; and 

 were it not for the text which describes the cellular depressions as five or six sided, 

 and the fact that no other spheroidal fossils having the surface marked by polygonaj 

 depressions are known from the horizon of the Niagara limestone, the forms we 

 have studied might never have been identified with Owen's species. The identifi- 

 cation was first made by Meek and VVorthen who, in the Geology of Illinois, Vol. 

 Ill, page 345, give the results of their study of this species under the name of 

 Pasceoliis? dactylioides Owen. They recognize the difference between the tornn 

 they describe and Billings' genus Pa sceolus, but without deciding the zoological 

 relationship of the form under consideration, and even without settling the ques- 

 tion of whether it was an external or internal cast, they propose for it the new 

 generic name of Cerionites. 



In the fourth volume of the Geology of Wisconsin, page 267, Prof. R. P. Whit- 

 field (-ffects another change in the spelling of the specific name, and discusses the 

 characters of the species in question under the head of Cerionites dacti/loides 

 Owen, although in the description of Plate XIII, Whitfield allows the name to 

 stand as Cerionites dactiloidcs. 



Concerning the specific name I think it must be evident that Owen intended to 

 use a term implying, not th.at the fossil described was like a finger, but that it was 

 like a ^/uwfc/e— something to put on the finger. The word that comes nearest to 

 standing for thimble may be spelled with our Reman letters dactulios from which 

 we may derive dactilioides, the form in which Ovsen probably intended to write it, 

 or dactglioides, the more correct spelling employed by Meek and Worthen. 



