.FOSSIL ECHINI OF THE PANAMA CANAL ZONE AND 



COSTA RICA. 



By Robert Tracy Jackson, 



Of Peterborough, Neio Hampshire. 



INTRODUCTION. 



The following is essentially a reprint of my paper bearing the 

 same title published in the Proceedings of the United States National 

 Museum, volume 53, pages 489-501, plates 62-68, September 24, 1917: 



The fossil echini of the Panama Canal Zone were submitted to me 

 for study and description by Dr. T. Wayland Vaughan as part of the 

 studies he is making in that region in connection with his investiga- 

 tions of the geology of the Costal Plain of the United States and of 

 the West Indies. The material contains some very interesting 

 species, particularly in the genus Encope, of which there are three 

 new forms. Some of the material is well preserved, and parts are 

 fragmentary. A number of specimens too poorly preserved, or too 

 fragmentary for specific determination, indicate that a more ex- 

 tensive echinoid fauna may be found by further search. 



I wish to express my heartiest thanks to my friend, Dr. Hubert 

 Lyman Clark, of the Museum of Comparative Zoology, who, with his 

 great knowledge of Clypeastroids and Spatangoids, helped me 

 materially in preparing this report. 



LIST OF SPECIES AND THEIR GEOLOGIC OCCURRENCE. 



Clypeaster lanceolatus Cotteau. Upper Oligocene, Emperador lime- 

 stone, Gaillard Cut, stations 58665, 6671. 



Clypeaster gatuni Jackson. Miocene, 1 Gatun formation, station 5662, 

 near Gatun Dam site ; and at station 6237, north of Ancon Hill, 

 about 4 miles south of Diablo ridge. 



Encope annectans Jackson. 1 Miocene, Gatun formation, station 

 5846, Spillway, Gatun Dam. 



Encope platytata Jackson. Miocene, 1 Gatun formation, station 

 6029a, one-quarter to one-half mile from Camp Cotton, toward 

 Monte Lirio. 



1 This formation is more appropriately referable to the lower Miocene, i. e., Burdigalian, 

 than to the upper Oligocene. — T. W. V. 



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