114 OUR COMMON BRITISH FOSSILS. 



channels which are excavated, so to speak, in the 

 under-surface of the limy plates, and thus reach the 

 mouth of the Encrinite beneath the plates, instead of 

 from above. The arms of Encrinites are not hollow, 

 as is sometimes supposed, but formed of solid joints, 

 or ossicles as they are scientifically called. The 

 joints of the stem, on the contrary, have a cavity 

 running down their middle, of various shapes, some- 

 times round, and frequently five-petal shaped. This 

 continuous hollow was formerly believed to be the 

 alimentary canal, but the notion is now considerably 

 modified. The joints of the stems of all species of 

 Encrinites are either grooved or toothed along their 

 margins. In this way they were firmly interlocked, 

 and yet were capable of such free movement that 

 there is no doubt the whole encrinital structure was 

 swayed about by the tides and currents as freely as 

 any of our large-rooted seaweeds. From what I 

 have said as to the pinnated arms of Crinoids, it will 

 be seen that the old notion of their being so many 

 nets in which to catch organic waifs and strays, is not 

 correct. In comparison with the size of the entire 

 structure the stomach is wonderfully small, and 

 enclosed in the large and densely plated body. Some 

 of the Carboniferous Encrinites must have had stems 

 of enormous length, judging from the strength and 

 diameter of the joints. In the Yoredale shales of the 

 valleys running from Hebden Bridge to Halifax, in 

 Yorkshire, I have obtained connected stems of 



