GEOGRAPHICAL DISTRIBUTION OF CORALS. 87 



to. the Gulf, occur a small but beautiful Fungia {F. elegans V.), 

 three Porites, a Dendrophyllia, a Pocillipora, some Astrangids, 

 and many fine Gorgoniae. The character of the species is 

 that of the cooler torrid region, rather than that of the warmer 

 torrid. 



Owing to the cold oceanic currents of the eastern border of 

 the Pacific — one of which, that up the South American coast, 

 is so strong and chilling as to push the southern isocryme ot 

 68^, the coral-sea boundary, even beyond the Galapagos, and 

 north of the equator — the coral-reef sea, just east of Panama, 

 is narrowed to 20°, which is 36° less of width than it has in 

 mid-ocean ; and this suggests that these currents, by their 

 temperature, as well as by iheir usual westwa7'd direction, have 

 ])roved an obstacle to the transfer of mid-ocean species to the 

 Panama coast. 



In the West Indies the reefs lie within the limits of the 

 isocryme of 74° F., or the torrid region ; and yet the variety 

 of species and genera is very small compared with the same 

 in the Central Pacific. The region contains some large Madre- 

 pores, the /)/. paimata, a spreading foliaceous species that 

 forms clumps two yards in diameter ; M. cervicornis, a stout, 

 sparsely-branched tree-like species, which attains a height of 

 fifteen feet ; M. proli/era, a handsome shrub-like species, of 

 rather crowded branches ; besides others ; and these are marks 

 of the existence of the warmer torrid region ; yet the sea has 

 not as high a temperature as the hottest part of the Pacific. 

 The species of the Astrsea tribe are few in number, and among 

 the largest kinds are the Maeandringe (the Diploria being here 

 included). None of the free Fungidae are known excepting 

 the two species in deep water, and none of the Pavonioe among 

 the compound species ; but the massive Siderinaj (Siderastr^ece) 

 are common, and the foliaceous Agaricias and Mycedia. Of 

 the Oculina tribe, species of Oculina, Cladocora and Astrangia 

 are relatively more numerous than in the Central Pacific ; but 

 there are none of the Pocilliporids, which are common bodi 

 in the torrid and subtorrid regions of the Pacific. Millei)ores 

 are very common. Gorgonice, are of many species. 



