238 bulletin: museum of comparative zoology. 



ECHINOSPHAERITES AND ChRISTLVNIA FAUNAS. 



The position of the Echinosphaerites beds in the American Ordovi- 

 cian section can not be said to be definitely established. The knowl- 

 edge which we have of these beds is due largely to Dr. Ulrich and to 

 Dr. Bassler (98), and by the former of these investigators the fossil is 

 reported as occurring at three horizons, one below and two above the 

 Lowville. 



The evidence concerning the younger of these occurrences, in so far 

 as it has been published, may be found in the description by Stose, of 

 the Chambersburg — Mercersburg map-area, and in the Revision of 

 the Palaeozoic Systems by Ulrich. The following section (here re- 

 arranged) is given by Stose (118). 



Feet. 

 10. Soft yellowish green sandstone with few fossils, said to 



be of Eden species 1200=*= 



9. Black carbonaceous shale, with Climacograptus spinifer, 

 Corynoides calicularis, Leptobolns insignis, Triarthrus 

 becki, etc., in lower 100 feet. 800 ± 



8. Shale and thin-bedded limestone with many small 

 fossils, including Triarthrus becki, Cryptolithus tessella- 

 tiis, Ampyx, Caryocaris, etc. 150=^ 



All the above strata are referred to the Martinsburg shale. 



7. Calcareous shale and shaly limestone, with Christiania 

 trentonensis, Pledambonites asper, P. pisum, Oxoplecia, 

 Parastrophia hemiplicata, etc. Echinosphaerites in the 

 upper ten feet. 150='= 



6. Dark gray, largely thin-bedded limestone with Nidu- 



litesfavus, Ampyx, Pledamboyviies asper, etc. 237=*= 



.5. Dark gray limestone in which Echinosphaerites is very 

 common, Ampyx, Receptaculites, Oxoplecia, and 

 brachiopods also common. 60=*= 



4. Grayish dense thin-bedded limestone with Tetradium 



cellulosum, Zygospira rccurvirostris, etc. 150=*= 



These limestones above are all grouped as the Chambersburg 

 limestone. 



