370 BATHYMETRICAL AND GEOGRAPHICAL DISTRIBUTION. 



At a depth of about 140 fathoms, extending to over 310 fathoms, are 

 found most interesting species : — 



Hemipedina cubensis. Echinus norvegicus. 



Podocidaris sculpta. 



While near the lowest depth reached hy the above species we strike 

 upon a peculiar fauna recalling types of the cretaceous period, extending 

 from 315 fathoms to the greatest depth attained in the straits between 

 Florida and Cuba. These are 



Salenia varispina. Homolampas fragilis. 



Pourtalesia miranda. 



Two species — Echinocyamus pusillus and Mellita sexforis — have the 

 greatest bathymetrical range, extending from the shore, the one to 270 

 fathoms and the other to 325 fathoms. I would state, however, that it is 

 only the young which have this great range ; the adult specimens are 

 limited to a quite shallow zone, — about 40 fathoms. In the young of our 

 common northern Cuvieria the reverse takes place, the young being quite 

 common at low-water mark, while young Echinarachnius and S. Drobachien- 

 sis are found at a much greater depth than the adult. 



I have given the greatest depth of living young, as the dead tests may 

 have been dropped by fishes or carried by currents. The character of the 

 Echinian fauna, on the three belts developed by the soundings of Mr. Pour- 

 tales, are tolerably well defined ; the first zone being littoral, and extending 

 to 90 fathoms, is characterized by species, the majority of which do not 

 range beyond 40 fathoms, with a few species ranging somewhat beyond, to 

 about 120 fathoms. 



The second zone (from 90 to 250 fathoms) is characterized by species ex- 

 tending into the first somewhat, and attaining a range of about 270 fathoms, 

 with an admixture of a few species extending from 140 to 310 fathoms. 



The third zone contains the typical deep-sea species of Florida, extending 

 from 315 to 500 fathoms. 



Although we have not a sufficient number of soundings to establish homo- 

 geneous zones of geographical and bathymetrical range, an analysis of the 

 above grouping of species shows us something analogous to the distribution 

 of animal and vegetable life in latitude and height ; the oceanic distribution 



