170 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



lancet-plate more or less completely concealed by side-plates. Deltoids very 

 small, generally confined to the upper face of the calyx, and seldom visible in 

 a side-view. Spiracles and hydrospires as in the preceding. Lower and 

 Middle Devonian ; Eifel, Ardennes, Spain, Great Britain and North America 

 (Hamilton Group of Indiana, Michigan, Canada). P. pailletti de Vern.; F. 

 eifelianus Roemer ; F. davatus Schnitze. 



Family 3. Troostoblastidae Etheridge and Carpenter. 



Calyx elongate. Ambulacra narrow, linear, deeply impressed, descending out- 

 ward from the summit. Deltoids confined to the narrow upper end, rarely visible 

 A externally, except the posterior one in Troostocrinus. Lancet- 



plate entirely concealed by side-plates. Spiracles distinct, repre- 

 sented by lineal slits at the sides of the deltoid ridge, and 

 bounded by deltoids and lancet-plates, but not by side-plates. 

 Silurian to Lower Carboniferous. 



Troostocrinus Shum. (Clavaeblastus Hambach) (Fig. 

 264). Calyx narrow, elongate, somewhat fusiform, with 

 contracted, subtruncate, or slightly convex upper face. 

 Ambulacra short. The four anterior deltoids overlapped 

 by the radial limbs ; the posterior one much larger than 

 the rest, and appearing externally. Posterior spiracles 

 conflueht with the anus. Silurian (Niagara Group) ; 

 North America. 



Metablastus E. and C. (Fig. 258, C). Like the preced- 

 ing, 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 am- 

 bulacrum. Devonian to Lower Carboniferous (Keokuk 

 Group) ; Europe and North America. 



Tricoelocrinus M. and W. (Saccoblastus Hambach). Calyx 



ir an+sp 



Fig. 264. 



Troostocrinus reinwarm pyramidal, broadest below and narrowing upwards ; when 



(Troost). Silurian 



nessee.^, Calyx from anal ggen from abovc or below stroudv pentaeronal in outline, 



side. B, Snmmit aspect. . .. i.ii r ^ 



(Z, Deltoid ; ir, Deltoid of owing to the projectmg and carinated character oi the 



anal side (after E. and C). j-i t\ ii. -j n i,i 



radials. Deltoids small ; ambulacra 

 long, and extremely narrow. Spiracles ten, distinct ; anus 

 large. Hydrospires small, enclosed within the substance of 

 the forked plates. Lower Carboniferous (Warsaw Group) ; 

 North America. 



Family 4. Eleutherocrinidae Bather. 



Elongate, stemless, asymmetrical, with four narrow ambulacra ; 

 fifth ambulacrum shortened and widened. Hydrospires not con- 

 centrated. Devonian. 



Eleutherocrinus Shumard and Yandell (Fig. 265). 

 Devonian (Hamilton Group) ; Indiana, Kentucky, New York and Canada 



Fk;. 'Mb. 

 Eleutherocrinus casse- 

 dnyi (Shum. and Yand.). 

 Lower Devonian ; Ky. 

 Ventral surface, -/i 

 (after E. and C). 



Family 5. Nucleocrinidae Bather. 



Calyx usually globular or ovoidal, with flattened or concave base, and linear 

 ambulacra extending the whole length of the calyx. Spiracles distinctly double, and 



