AGASSIZIA EXCENTRICA. 73 
nus, Astropyga, and other Diadematidas and Echinothuria; ; in the last, there 
is, as I have shown, even what we might consider in some cases a regular 
marginal fasciole, as in Phorniosoma. The miliary granulation of the Cly- 
peastroids generally, and the comparatively small radioles they carr^y, may 
according to this view be considered as embryonic features which have 
become greatly specialized, the whole test retaining the granular tubercula- 
tion characteristic of the earlier Crinoids, with but slight modifications in the 
fasciolar radioles covering the whole test, if I may so call them, while they 
become, strictly speaking, minute primary or secondary radioles. 
Although in the young stages of such Spatangoids as Hemiaster, Bris- 
sopsis, Schizaster, and the like, the fascioles make their appearance very 
early, yet in this youngest stage of Agassizia there is at a corresponding 
period no well-defined fasciole band, and it is only in a somewhat more 
advanced stage (4 mm. long, diam.) that we get a clearly defined fiisciole. 
This seems to affect the character of the spines found above and below it, 
and we have in the stage just mentioned a well-defined lateral marginal 
fasciole close to the ambitus. This fasciole is in reality only an extension of 
the subanal fasciole, such as Ave find a remnant of in Argopatagus. The 
peripetalous fasciole is also developed, and its anterior extremity comes down 
close to the ambitus, as it does in Paleopneustes. 
In the youngest Agassizia (3 nun. long, diam.) there are three or four 
single pores forming the rudimentary petals of the lateral ambulacra. The 
apical system is represented in this stage merely by the large madreporic 
body which covers the whole apex. The surface of the test in these younger 
stages, more especially in the ambulacral areas, is covered by numerous 
small-headed, short-stemmed pedicellaricB and by minute straight miliary 
spines, often club-shaped. 
In a specimen measuring 6 mm. in longitudinal diameter, the odd ante- 
rior ambulacrum was not yet developed at all ; the lateral arabidacra con- 
sisted of six and seven pores, the anterior ambulacra being composed of 
single rows of pores, the posterior ambulacra of double rows ; the anterior 
rows of the posterior ambulacra were made up of three small pairs of pores 
with a couple of single pores near the apex of the ambulacnmi. 
Meoma ventricosa Lutk. 
Florida Bank, and off Havana. 37-127 fathoms. 
