HARKNESS — THE GEOLOGY OF HOOK POINT. 



73 



stem, cup, arms, and thin net-like membranes retain all their original 

 perfection, and they appear as if they had been suddenly en-veloped 

 in some rapid deposition of mud, while they were resting from their 

 labours and digesting the food which their membraneous extremities 

 had caught. In some instances the stems are in such a condition as 

 to allow us to judge of the arrangement of the joints composing 

 them, as also of their flexibility. The surfaces of some of the strata 

 are covered by these stems, and sometimes the stems have such a 

 sinuous and convoluted aspect as to lead to the conclusion 

 that these crinoids covering the bottom of the carboniferous 

 sea, moved about under every influence of wave and current, as 

 trees do on land when a breeze is powerful enough to shake them. 

 Hook Point is equally celebrated for the remains of that tribe 

 of animals which is known under the name of Bryozoa, and 

 which in their internal structure have great affinity to animals 

 constructing and inhabiting bivalve-shells. Among these we have 

 Diastopora, a parasite, which lived and built its habitation on other 

 Bryozoa, forming a small patch of calcareous matter, having cells with 

 semicircular apertures pointing outwards. Glauconome — one form of 

 which presents a feather-like aspect, having a central shaft, from 

 whence issue numerous obliquely placed bars, running together 

 regularly, and leaving interspaces of an oval form, the bars having 

 on one side a row of pores along each margin — is seen in considerable 

 profusion. Polypora, a net-like form, having its under surface devoid 

 of pores, but with the upper surface covered with several rows of cells 

 on each of the upright bars, also appears at Hook Point. The form 

 of Bryozoa which occurs in the greatest profusion and perfection is 

 Fenestella. Several distinct species here make their appearance, and 

 in some cases the limestones appear to be almost altogether made up 

 of this form. It has a window-like aspect when magnified ] but, seen 

 without the aid of the microscope, has somewhat of a net-like 

 structure ; its under surface, like the Bryozoa generally, is devoid of 

 pores ; but the thicker upright bars have commonly a finely striated 

 surface. The upper side of the bars is usually marked by a central, 

 well-exhibited keel, and on the outer side of this are the numerous 

 pores from whence the heads of the animal inhabiting the Fenestella 

 issued. The thin cross-bars which serve to connect the thicker pore- 



