CHARACTERISTIC DEEP-SEA TYPES. SEA-URCHINS. 



97 



of proof that pedicellarise are merely modified spines. The only 

 other striking' genus among the regular urchins is that of Hemi- 

 pedina (Fig. 3G3), the modern repre- 

 sentative of a family once greatly de- 

 veloped in the cretaceous period. 



Althouo'h the line to the eastward 

 of Charleston, S. C, was commenced 

 off, the very home of the Scutellte and 

 other clypeastroids, it is remarkable 

 that not a sino'le Mellita or Clypeaster „. ,., „ . ,. 



was dredofed either on that line or the cubensis. \. 



line run in the axis of the Gulf Stream 



as far as Cape Hatteras. We had a similar experience while 

 dredging near the 100-fathom line when approaching the South 

 American continent. The clypeastroids are evidently shallow- 

 water types, with the exception of Echinocyamus, which extends 

 into deep water (805 fathoms), and Echinarachnius, living speci- 

 mens of which have come up in the trawl from a depth of 524 

 fathoms off George's Bank. An immense number of dead tests 

 of Echinocyamus pusillus were dredged in the Caribbean, the 

 Gulf of Mexico, and the Straits of Florida.^ 



The Nucleolidse, to which Neolampas (Fig. 364), Rhyncho- 

 pygus (Fig. 365), and Conolampas belong, are but scantily rep- 



r'i^-T^ T-5rT,5 ' 



Fig. 304. — Neolampas 

 rostellata. |-. 



^•^^>f:'i^-^0o}i'^^^:k^. 



Fig. ;>(>"). — Rhyiu-liopygus 



earibfearum. 



1 • 



resented in the echinid fauna of to-day. They were once among 

 the most numerous of the urchins, and flourished especially 



^ It is interesting to note, in connection opneustes, of Trigonocidaris, of Temne- 



with this, that dead tests of species of chinus, of Salenia, and of Cidaris, were 



Clypeaster, of Echinanthus, of Encope, also frequently dredged, and sometimes 



of Schizaster, of Macropneustes, of Tox- in considerable numbers. This has au. 



