CHARACTERISTIC DEEP-SEA TYPES. — SEA-URCHINS. 97 
of proof that pedicellarizo are merely modified spines. The only 
other striking genus among the regular urchins 1s that of Hemi- 
pedina (Fig: 363), the modern repre- 
sentative of a family once greatly de- 
veloped in the cretaceous period. 
Although the line to the eastward 
of Charleston, S. C., was commenced 
off the very home of the Scutella and 
other clypeastroids, it is remarkable 
that not a single Mellita or Clypeaster 
^ 3 Fig. 262. — Hemipedina 
was dredged either on that line or the cubensis, 1 
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 Echinoeyamus, 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 Nucleolide, to which Neolampas (Fig. 364), Rhyncho- 
pygus (Fig. 365), and Conolampas belong, are but scantily rep- 
Fig. 364. — Neolampas Fig. 365. — Rhynchopygus 
rostellata. 4. earibmarum. 2:25, 
resented in the echinid fauna of to-day. They were once among 
the most numerous of the urchins, and flourished especially 
1 Tt 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 Sehizaster, of Maeropneustes, of Tox- in eonsiderable numbers, This has an 
