2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



ing about 30 species, largely new and belonging to new genera, 

 form the object of the present study. 



The writer is indebted to the American Philosophical Society for 

 grant No. 3454-P which defrayed field and laboratory expenses. He 

 thankfully acknowledges the enthusiastic cooperation of Dr. John M. 

 Bird in quarrying the limestone and searching for other fossiliferous 

 localities. Thanks are also due to Dr. A. R. Palmer for suggesting 

 this study and for valuable discussions on Cambrian faunas ; to Mr. 

 Thomas W. Talmadge for information on the results of his strati- 

 graphic studies in the East Chatham quadrangle and for accompany- 

 ing the writer on a field excursion; to Dr. George Theokritoff for 

 information on an undescribed Lower Cambrian faunule from Wash- 

 ington County, New York; to Dr. E-an Zen for discussions on the 

 Taconic sequence ; and to Mr. A. W. A. Rushton of the British 

 Geological Survey for communicating specimens and photographs of 

 an undescribed faunule from England which shows interesting affini- 

 ties with the one described herein. 



OCCURRENCE AND PRESERVATION OF THE FOSSILS 



The Cambrian strata in the northwestern quarter of the East Chat- 

 ham 7^-minute quadrangle are notable for the development of regu- 

 larly bedded limestone units, an unusual feature in the Cambrian 

 of the Taconic sequence in Columbia and Rensselaer Counties, New 

 York, where fossiliferous limestone generally occurs only in con- 

 glomerates. Among the localities where such limestone beds form 

 outcrops is a hill (Griswold farm) about 1 mile southeast of North 

 Chatham, Columbia County. The summit of the hill is a plateau 

 where limestone beds interstratified with black shale form scattered 

 outcrops. The beds strike north-south and dip steeply (50°-60°) 

 east. All the fossils described herein (with the exception of one 

 species from Quebec, Canada) were recovered from a limestone bed 

 traceable through intermittent outcrops over a distance of several 

 hundred feet. Even though fossils of the same faunule were observed 

 at several places along this bed, only one block of limestone, about 

 1 foot thick, 5 feet long, excavated to a depth of 3 feet, supplied 

 all the described fossils, the remainder of the limestone usually being 

 too fine-grained to yield fossils. About 400 pounds of rock were 

 removed and examined. The limestone is dark-gray, finely granular 

 to aphanitic, in some portions the bedding being clearly marked by 

 layers of more abundant insoluble material or fossil fragments, else- 



