72 
THE GEOLOGIST. 
approach to vegetables, but which in their portions possessing the 
power of sensation have the simplest animal organization — we find the 
Astrceopora, with its slightly convex surface covered over with stellate 
pores, the former abode of the numerous-headed animal which con- 
structed the strong fabric forming its habitation. Here, too, occurs 
the Aulopora, with its chain-like form, spreading itself over the sur- 
faces of shells, and studded on its upper side with numerous aper- 
tures from whence issued the heads of its occupant. The Michelina, 
with its surface covered with depressed stars, arranged in an hexagonal 
form like an antique pavement, here, too, makes its appearance in 
considerable abundance; Stenopora, with its branching form and rugose 
surface, here also occurs ; and among them also we find Zaplm-entis, 
which, when broken perpendiculai'ly, exhibits a structure like a series of 
small funnels piled one upon another in its intei'ior. 
Hook Head is, however, more famous for its Crinoids— those ancient 
stem-like stone-lilies endowed with animal organization, and which 
flourished in such great abundance in many of the paleozoic seas ; 
numberless fragments of these forms occur, for the most part in the 
state of fragments of stems ; sometimes in the form of the cup- 
plates, and instances are not uncommon of almost perfect specimens 
being found. 
One of the forms of crinoids, Actinocrinus, makes its appearance 
generally in the condition of detached plates ; sometimes we have the 
cup in a state of perfection showing the base composed of its three 
pieces of qiiadrangular form, surmounted by numerous hexagonal 
plates, and terminated by arms which branch in a dichotomous 
manner. Cyathocrinus, too, occurs here, with its cup-base composed 
of five pieces supporting five other larger plates, which form the 
principal mass of the cup, and the base from whence the arms 
emanated. Platycrinus also abounds, with its base composed of three 
plates, surmounted by five larger pieces, which immediately support 
the base from whence the dichotomous ones arise. Poteriocrinus, 
with its five basal pieces, and its five subradial fragments, and long 
branching arms, here is met with. Ehodociinus also is seen, with its 
numerous plates beautifully fitted together, and looking, in some 
species, like a rugose seed studded over with tubercles. It frequently 
happens that here we meet with an individual crinoid in which the 
