218 PANAMIC DEEP SEA ECHINI. 



BATHYMETRICAL AND GEOGRAPHICAL RANGE OF THE PANAMIC AND 

 WEST INDIAN ECHINID PAUN-53. 



In 1895 Koehler 1 called attention to the small number of new and strik- 

 ing forms of Echini collected by the more recent deep-sea expeditions as 

 compared to the many new types collected by the " Challenger " and the 

 "Blake." The material of the " Travailleur " and "Talisman" has not 

 as yet been published, but the number of species is known to be small, 

 and perhaps the limited field explored by the French expeditions may 

 account for this dearth. The same is true of the "Valdivia" Expedition 

 in the Indian Ocean and the Antarctic expedition of the " Belgica." The 

 "Siboga" expedition, however, which explored a region with one of the 

 richest Echinid fauna 1 , collected no less than thirty-one new species of 

 Echini, forming quite a percentage of the known species, of which M. de 

 Meijere says twenty-four are deep-sea species. The most interesting species 

 are four allied to such genera as Paleopneustes, Linopneustes, and Am- 

 phipneustes, one of the Pourtalesiae, and one of the Ananchytidse allied to 

 Urechinus. We can hardly call twenty-four of them deep-sea species, as 

 no species has been obtained at a greater depth than 1000 fathoms, and 

 only thirteen species below a depth of 500 fathoms. Still the range of 

 many of the genera collected by the " Siboga " has been shown to vary 

 between much shallower depths than was supposed to be the case. From 

 the physical conditions of the region explored it was natural that the char- 

 acteristic Echini collected should belong to the continental slope. 



The '"Albatross" expedition of 1891, trawling along and beyond a con- 

 tinental range, but in deeper water than the " Siboga," collected in the 

 limited area explored a large number of deep-sea types, no less than 

 twenty-five species, — six species within the 400-fathom line; one species 

 within the 700-fathom line; two species within the 1000-fathom line; two 

 species within the 1200-fathoin line ; the other fourteen within the 1900- 

 fathom line. 



No collections of Echini were made in shallow waters, except on the reef 

 at Panama Harbor, where a few specimens of Arbacia stellata and of Cidaris 

 Tkouarsii were obtained. 



In a chapter on the Origin of the West Indian Echinid Fauna 2 I have 



1 Xote pre'l. sur les Echinides recueillis pendant les Campagnes de l'Hirondelle. Bull. Soc. Zool. 

 de France, 1895, p. 22. 



2 " Blake " Echini, p. 79. 



