212 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



the Emperador limestone is represented as dipping below the Gatun 

 formation on the north side of the Isthmus, and it is exposed almost 

 down to the sea level on the south side. The Culebra formation 

 underlies the Emperador limestone on both slopes, but it is not indi- 

 cated on the map on the north slope of the Isthmus. 



Miocene. 



BOWDEN MARL.i 



The point of departure in the consideration of the Miocene is the 

 fauna of the Bowden marl of Jamaica. The following is a revised 

 list of the species: 



Placotrochus costatus Duncan. 



Sphenotrochus new species. 



Placocyathus barretii Duncan. 



alveolus (Duncan.) 



StylopJiora granulata Duncan. 



Aster osmilia profunda (Duncan). 

 Jiitli Vaughan. 



StepJianocoenia intersepta (Esper), also living. 



Antillia walli Duncan. 



Thysanus excenlricus Duncan. 

 elegans Duncan, 

 new species. 



Syzygopliyllia gregorii (Vaughan). 



Siderastrea siderea (Ellis and Solander), also living. 



Goniopora new species. 



Pontes baracodensis Vaughan. 



Acropora new species. 



This fauna indicates somewhat deeper water than that in which 

 the species mentioned on preceding pages lived; but the presence of 

 StepJianocoenia intersepta, Siderastrea siderea, Acropora new species, 

 a massive species of Goniopora, and Poriies baracodensis, furnish evi- 

 dence in favor of the conclusion that the 'depth probably was not so 

 much as 20 fathoms. The most striking feature of this list is that it 

 contains the names of two species still living in the Caribbean region, 

 in this respect differing from all the other faunas previously consid- 

 ered in this paper. The Bowden not only marks the introduction of 

 species that persist in the West Indian region, but as neither in 

 Jamaica, Santo Domingo, nor Cuba, have species of Astrocoenia, 

 Siylocoenia, Leptomussa, Antiguastrea, Favites, Leptoria, Troclioseris, 

 Leptoseris, Haloseris, Pironastraea, MesomorpTia, CyathomorpTia, 

 Diploastrea, Astreopora, Aciinacis, or Poriies (Synaraea) been found 

 in beds of the same age as or younger than the Bowden, these 



1 For an account of the stratigraphic relations of the Bowden mar], see Hiil, R. T., The geology and 

 physical geography of Jamaica, Mus. Comp. Zool. Bull., vol. 34, No. 1, pp. 226, with 35 plates, lS9f 

 (especially pp. 82-86, 145-152). 



