48 [Proc. B.N.E.C , 



the summit of the test, to near the mouth, which is opposite 

 to it. The masticating apparatus of some urchins is very com- 

 plicated, and is commonly known as Aristotle's Lantern. The 

 teeth are constantly growing to make up for wear. Other 

 urchins have no teeth at all, but instead have the mouth 

 produced into a tube, by means of which they burrow in the 

 sand, in which they live and from which they extract what 

 nutriment they can. The organs of locomotion are tube feet ; 

 these are furnished with sucking discs, and the urchin is able, 

 by attaching them to some object, to pull itself forward. Pro- 

 gression is sometimes made by the urchin rolling over and 

 over, fresh relays of tube feet coming into action all the time. 

 A few species of urchin are able, for their protection, to 

 excavate hollows in the solid rock. A well-known example 

 of this is Strongylocentrotus lividus, an inhabitant of the 

 rock-pools at Bundoran and other places on the West Coast 

 of Ireland. They are mostly associated with a coralline, 

 which covers the rock in the space between the burrows, some- 

 times to a height of 1| inches, and often makes the urchin a 

 prisoner in its own house, growing partly over the holes. Sea 

 urchins are of great geologic age, being found in the Ordo- 

 vician rocks in Russia. They were very abundant in Jurassic 

 and Cretaceous times, thirty genera being known from the 

 latter system. Some of these genera, such as Cidaris, still 

 inhabit our seas. 



The next paper was by Mr. Nevin H. Foster on 

 " Feathers." After some introductory remarks, Mr. Foster 

 explained that feathers are not distributed over a bird's body 

 in the same way as are the hairs on mammals. The hairs of 

 a horse are set closely together all over the body, whereas the 

 feathers of a bird are restricted to certain well defined tracts, 

 with bare spaces of naked skin between. The body is only 

 concealed from view because the feathers are long and broad, 

 and are so directed as to slope away from a line drawn through 

 the middle of any given tract. These tracts — discovered sixty 

 years ago by a German ornithologist named Nitzsch — and the 

 regular nature of their distribution over the body have led to 



