the Morphology of the Blastoidea. 419 
writers have all added more or less to our knowledge of this 
interesting but difficult group. Although some of their con- 
clusions have not borne the test of further investigation, yet 
their observations have been mostly confirmed by later workers, 
while their descriptions of them are clear, accurate, and scien- 
tific. ‘Two other palxontologists have recently taken up the 
subject, and have treated it in very different ways, as I 
propose to show in the following pages. 
Mr. Charles Wachsmuth, of Burlington, Iowa, who is so 
well known by his writings on the Paleocrinoids, has pub- 
lished incidentally, in the revision of that group by himself 
and Mr. Springer, some extremely valuable notes on the 
structure of the Blastoids, which are illustrated by excellent 
diagrams *., The chief novelty discovered by him is the 
presence in Pentremites of a plate lying directly below the 
lancet-piece, with a tubular passage running through it. He 
does not, however, either describe or figure any perforation of 
the lancet-piece itself; and in the case of Granatocrinus he 
merely figures one subambulacral f plate, pierced by a longi- 
tudinal canal. 
Dr. Hambach f, on the other hand, figures a section of a 
ray (of Granatocrinus Norwoodi ?), the lancet-piece of which 
is not only “ pierced through the centre in its whole length 
by a very fine canal,” but also has a posterior (se) side which 
is ‘“ concave, semilunar, and grooved in its whole length for 
the reception of some duct or vessel.” At the summit this 
duct or vessel “connects with a circular duct (cesophageal 
ring ?), surrounding, on the interior side, the central orifice or 
annulus centralis.” ‘Thanks to the kindness of Mr. Wachs- 
muth, I have been enabled to examine many beautiful inter- 
nal casts of Granatocrinus Norwoodi, a well-preserved speci- 
men of which is the original of Dr. Hambach’s description ; 
but, despite this advantage, I am at a loss to understand his 
* Part I. of the “ Revision of the Paleeocrinoidea” appeared in the 
‘Proceedings of the Philadelphia Academy’ for 1879; and Mr. Wachs- 
muth has been good enough to favour me with advance sheets of Part IL., 
which will be issued shortly. In this valuable work the authors have 
reduced the chaos of the Paleeocrinoids to something like order; and the 
illustrated memoir, of which it is but the precursor, will be heartily 
welcomed in Europe, as it is utterly impossible to gain clear ideas about 
many of the American species, owing to the difficulty of obtaining the 
literature on this side of the Atlantic. ; 
+ LI use this word simply to denote the parts beneath the food-groove, 
without thereby implying any homology with similarly-named structures 
in the Kchinozoa. 
¢ “Contributions to the Anatomy of the Genus Pentremutes, with De- 
scriptions of new Species,” Trans. St. Louis Acad. vol. iv. no. 1, pp. 145- 
160. 
