REPORT ON THE CRINOIDEA. 193 



supposed arms and pinuules 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 JMiller, 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 Pelmatozoa, 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 liber 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, i.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 

 Eande des Kelches noch besondere zahkeich gegliederte Arme sich vorfinden, deren 

 Skeletstiicke immer dem Perisom angehoren und stets von dem dorsalen Pole ihren 

 Ursprung nehmen." In this description of the Crinoids, as w^ell as in the prominence 

 given to the presence or absence of a stalk in the morphology of the Echinodenns, 

 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 Ciinoid lies on its 

 aboral surface, instead of creeping about mouth downwards in search of food. The lateral 



1 Palfeontology of New York, 1S52, vol. ii. p. 191, pi. xlii. figs. 5, 6. 

 - Catalog. Camb. Silur. Foss. VVoocItv. Mus., Cambridge, p. 118. 



5 Ueber die Morphologie und die Verwandtscliaftsverhaltnisse der wirbellosen Thiere, Braunschweig, 1848, p. 42. 

 (ZOOL. CHALL. EXP. — PART XXXII. — 1884.) Ii 25 



