192 ECHINODERMATA—PELMATOZOA SUB-KINGDOM III 
be noted, are frequently effaced in weathered specimens (Fig. 315, 4 and B).* 
Small pit-like depressions, or small tubercles, which are observable on the side- 
plates, indicate the places where the appendages or pinnules were formerly 
attached. These are 
only exceptionally 
found intact, but 
when preserved they 
completely conceal 
theambulacral fields, 
and extend upward 
above the summit of 
the calyx (Fig. 316). 
They vary consider- 
ably in length, even 
among species be- 
longing to the same 

Fic. 317. 

Pentremites sulcatus, Say. Sub- 
Fic. 316. Carboniferous; Illinois. Trans- genus, 
a, Pinnule of Pentremites, enlarged ; verse section of calyx at about 1/3 : 
b, Granatocrinus Norwoodi, O. and 8., the height of the ambulacral fields. In most Blastoids 
with perfectly preserved pinnules (after xX 11/o. hy, Hydrospires ; 1, Lancet- Salm 
Meek and Worthen). plate ; p, Pore-plates; 7, Radials. the side plates, or 
the outer side-plates 
when such are present, are pierced by marginal pores (or hydrospire pores), which 
communicate with the hydrospires. The pores are situated at the extreme 
outer margins of the plates, at the end of the lateral ridges, and alternate in 
position with the sockets of the pinnules. They are present in all forms, 

Fie. 318. 
Transverse sections through the ambulacral fields, showing various forms of hydrospires. A, Granatocrinus 
Derbyensis. B, Granatocrinus Norwoodi. C, Metablastus lineatus. D, Orophocrinus verus. All sections enlarged 
(after Etheridge and Carpenter). 
having the hydrospires concealed within the calyx; but are absent in the 
Codasteridae, in which the hydrospires are wholly or in part exposed on the 
outer surface. 
The hydrospires are bundles of flattened, lamellar tubes, extending under- 
' [According to Wachsmuth these markings are not a mere ornamentation ; but the ridges consti- 
tute the sides, and the depressions the floors of a series of small ducts leading from the pinnules to 
the median ambulacral groove. In a number of excellently preserved specimens observed by this 
distinguished author (Pentremites, Orophocrinus, and Schizoblastus), not only the longitudinal groove, 
but also the side grooves throughout the entire field were roofed over by alternately arranged, very 
minute plates, extending all the way to the pinnules. The arrangement of the side duets, their 
upward curvature on approaching the main canal, and their relations to the pinnules, leaves scarcely 
a doubt that they were closed food-grooves serving to conduct nutriment from the pinnules to the 
mouth. 
It is questionable whether the term “ pinnules ” is strictly appropriate as applied to the appendages 
of Blastoids, for while the latter evidently performed the function of arms, it is by no means certain 
that they discharged the ova, which is the special office of pinnules in Crinoids. The statement that 
the appendages are frequently biserial does not agree with the observations of Wachsmuth. All the 
specimens examined by this writer are uniserial, but the ossicles are sometimes sharply wedge-shaped, 
and interlock to a slight extent from opposite sides, thus simulating a biserial arrangement.—TRANS. } 
