ORDER I BLASTOIDEA—REGULARES 195 
Spiracles, as a rule, distinctly double, 
Lancet-plate perfectly, or for the most 
Belgium, England, North 
very narrow, extending to the base. 
but sometimes incompletely divided. 
part, concealed by side-plates. Carboniferous ; 
America. JM. crenulatus, Roemer. 
Troostoblastidae. 
Family 2. Etheridge and Carpenter. 
Ambulacra narrow, linear, deeply impressed, descending outward from the sumnut. 
Deltoids confined to the narrow upper end, invisible externally, eacept the posterior one 
in Troostocrinus. Lancet-plate entirely concealed by side-plates. 
Spiracles distinct, represented by lineal slits at the sides of the deltoid 
ridge, and not bounded by side-plates. Silurian to Sub-Carbon- 
iferous (Warsaw Group). 
Troostocrinus, Shum. (Fig. 321). Calyx narrow, elongate, 
somewhat fusiform, with contracted, subtruncate, or slightly 
convex upper face. Ambulacra short. The four anterior 
deltoids overlapped by the radia limbs; the posterior one 
much larger than the rest, and appearing externally. Posterior 
spiracles confluent with the anus. Silurian (Niagara Group) ; 
North America. 
Metablastus, E. and C. Like the preceding, but all the 
deltoids equal, and the two posterior spiracles not confluent 
with the anus. Spiracle slits ten in number; hydrospires 
four to each side of an ambulacrum. Silurian to Sub-Car- 




4 (11047; 
KES 
a / 
Fic, 321. 
Troostocrinus Rein- 
boniferous. 
Tricoelocrinus, M. and W. Calyx pyramidal, broadest below 
and narrowing upwards ; when seen from above or below, 
strongly pentagonal in outline, owing to the projecting and 
carinated character of the radials. Deltoids small ; ambulacra 
long, and extremely narrow. 
tinct ; anus large. 
Carboniferous. 
Nucleoblastidae. 
Carpenter. 
Family 3 
whole length of the calyx. 
lancet - plate and deltoids. 
Carboniferous. 

Sub-Family A. ELAEACRINIDAE. 
Carpenter. 
Elaeacrinus Verneuili, 
Troost sp. 
Columbus, O. (after 
A, Side-view of calyx. 
C, Ventral surface. D, Same, 
Lower Devonian ; 
Roemer). 
B, Base. 
enlarged. 
plate. 
Elaeacrinus, Roemer (Nucleocrinus, Conrad), (Fig. 322 
within the substance of the forked plates. 
wardti, Troost sp. 
Silurian ; Tenn. 
(after Roemer). 
A, Calyx from one 
siae (nat. size). 
B Summit aspect 
(enlarged). 
Spiracles ten, dis- 
Hydrospires small, enclosed 
Sub- 
Etheridge and 
Calyx usually globular or ovoidal, with flattened 
or concave base, and linear ambulacra extending the 
Spiracles distinctly double; 
and chiefly formed by the apposition of notches in the 
Devonian 
and Sub- 
Etheridge and 
Posterior deltoid divided into two parts by an anal 
Anus distinct from the posterior spiracles. 
Basals small, 
inconspicuous, sometimes hidden within the columnar cavity. Radials small, 
