REPORT ON THE CRINOIDEA. ils} 
supposed arms and pinnules which were described by Hall as Myelodactylus* as a coiled 
up stem of peculiar structure. It may perhaps belong to some Crinoid of which the 
head is not yet known; but until Salter’s statements” have been satisfactorily refuted 
by Hall or Miller, I cannot admit the Myelodactyloidea as a class of Echinoderms 
equivalent to the Crinoidea, Ophiuroidea, or Blastoidea. 
The Echinoderms which have no tube-feet in their ambulacra, and are more or less 
permanently attached by their aboral surface, seem to me therefore to fall very naturally 
into three classes, Crinoidea, Cystidea, and Blastoidea. They have several characters 
in common which sharply distinguish them from the other Echinoderms, and serve to 
define the branch or division Prtmarozoa, Leuckart, which is of course synonymous 
with Crinoidea in the widest sense. 
I am indebted to my friend Prof. F. Jeffrey Bell for the reference to Leuckart’s 
original definition of the group. I heard the name first from Sir Wyville Thomson, who 
was greatly struck with its appropriateness, and introduced it into the syllabus of his 
class lectures. He could, however, give me no reference to it; but Prof. Bell was 
fortunately able to find it in Leuckart’s Bericht iiber die wissenschaftlichen Leistungen 
in der Naturgeschichte der niederen Thiere for 1864-65, where the Echinoderms are 
divided into Pelmatozoa, Echinozoa, and Scytodermata (Holothurians). Working back 
from this year Prof. Bell eventually succeeded in tracing back this classification of 
Leuckart’s to a morphological essay published in 1848, where, however, the familiar name 
Actinozoa is used to denote the Urchins and Starfishes together. After alluding to the 
essential characters of the Pelmatozoa, z.e., the presence of a stem either temporarily or 
permanently, Leuckart referred to the two orders of this class, the Cystids and the true 
Crinoids.? The latter is distinguished by the fact that “‘ An dem obern peripherischen 
Rande des Kelches noch besondere zahlreich gegliederte Arme sich vorfinden, deren 
Skeletstiicke immer dem Perisom angeh6ren und stets von dem dorsalen Pole ihren 
Ursprung nehmen.” In this description of the Crinoids, as well as in the prominence 
given to the presence or absence of a stalk in the morphology of the Echinoderms, 
Leuckart seems to me to have been peculiarly fortunate. The only point to which one 
might be disposed to take exception, and it is in reality more a verbal one than anything 
else, is his description of the arm-skeleton as belonging to the perisome; for the term 
“ perisomatic” skeleton is now somewhat limited in its meaning (ante, p. 73). 
The Pelmatozoa therefore differ altogether from other Echinoderms in the presence 
of a stem, and in the consequent departure from the ordinary habits of an Urchin, Star- 
fish, or Holothurian. Whether sessile, or provided with a stem, the Crinoid les on its 
aboral surface, instead of creeping about mouth downwards in search of food. The lateral 
1 Paleontology of New York, 1852, vol. ii. p. 191, pl. xlii. figs. 5, 6. 
2 Catalog. Camb. Silur. Foss. Woodw. Mus., Cambridge, p. 118. 
3 Ueber die Morphologie und die Verwandtschaftsverhaltnisse der wirbellosen Thiere, Braunschweig, 1848, p. 42. 
(ZOOL, CHALL. EXP.---PART XXX1I.—1884.) Ti 25 
