somp: pp^culiar spiral fossil forms from 

 california and mexico 



By Wendell C. Mansfield 

 Of the United States Geological Survey 



In 1927 I described some peculiar fossil forms from the Miocene 

 (?) of Maryland.^ Subsequent to the publication of that paper Dr. 

 iJruce L. Clark, of the University of California, Berkeley, Calif.,, 

 sent me specimens of similar fossil forms from California and Mex- 

 ico, and he has kindly permitted me to describe them. 



The Maryland specimens are spiral, nearly straight, and irregular 

 objects, probably representing the remains of organisms. They 

 were obtained from the low bluffs along the western shore of Chesa- 

 peake Baj, St. Marj^s County, Md. For the spiral form I proposed 

 a new generic name, Xenohelix, and designated Xenohelix mary- 

 landica Mansfield as the genotype. I said that I had not formulated 

 any particular theory to explain the origin of the coiled or uncoiled 

 forms. I also mentioned that if these forms owe their origin to 

 some organism, as they probably do, that of some marine plant, per- 

 haps a fucoid, seems the more likely. I have obtained no additional 

 information to explain the origin either of the Maryland specimens 

 or the specimens described in this paper. Neither do I know that 

 the specimens obtained in so widely separated areas have the same 

 origin. 



DESCRIPTION OF TWO NEW SPECIES 



I have placed the following two new species provisionally under 

 the genus Xenohelix^ although they may have no generic relationship 

 to the Maryland form. 



XENOHELIX? CLAKKI, new species 



Plate 1, Figure 1 



The specimen selected as the holotype is incomplete, the whorls 

 at either extremity having been broken away. It consists of four 



^U. S. Nat. Mus. Proc, vol. 71, No. 268S, art. 16, 1927. 



No. 2836.— Proceedings U. S. National Museum, Vol. 77, Art. 13. 



2598—30 1 



