LECTURES ON MOLLUSCA. 19 



Canada when they lay at the bottom of the palaeozoic seas, it would 

 have encountered multitudes of long pointed shelly cones, floating 

 upright in the water, some of them adorned with beautiful colors and 

 sculpture, and slowly moving among the corals, sea-weeds, and stone- 

 lilies which then adorned the gardens of the great deep. They be- 

 longed to the 



Family ORTHOCERATID^:, 



or Straight-horns. Some of them carried on their backs the largest 

 shells that ever lived. A specimen belonging to Col. Jewett, of Albany, 

 now measures twelve feet, and when perfect must have been fifteen feet 

 in length. And yet, from the buoyancy of its contained air, the com- 

 paratively feeble cephalopod could maintain its enormous leverage, and 

 crawl on its slender tentacles. The aperture of the Orthoceratites is 

 generally contracted, and the head was perhaps always exposed. The 

 siphuncle is very large, and in some of the genera very curiously formed, 

 indicating much more vitality than in the corresponding part of the 

 Spiral Nautilus. This was necessary in order to maintain a living con- 

 nection at such a distance from the body. All the orthoceratites have 

 simple, concave chambers, with a central opening. They disappear at 

 the beginning of the secondary rocks, leaving their work to be per- 

 formed by the huge Ammonites of the Lias. In Gonioceras, the shell is 

 flattened, and the septa waved. In Actinoceras , Hormoceras and Hu- 

 ronia, the siphuncular processes are enormously developed around the 

 central tube, according to different patterns. In Thoracoceras and 

 Cameroceras, the siphuncle is marginal, and generally small. The 

 strange fossils called Endoceras by Prof. Hall have very long slender 

 shells, with a large cylindrical siphuncle, somewhat lateral. This is 

 thickened internally by separate layers of shell, or funnel tubes one 

 inside the other, called " embryo tubes" by the author, contrary how- 

 ever to all analogy. Their use may have been to give increased strength 

 in consequence of the great elongation of the shell. Some of the species 

 appear to have been constituted from the accident of a young shell being 

 lodged in the siphuncular cavity : others from the monstrous formation 

 of a second siphuncle. 



Thanks for the heavenly message brought by thee, 



Child of the wandering sea, 



Cast from her lap forlorn ! 

 From thy dead lips a clearer note is borne 

 Than ever Triton blew from wreathed horn! 



"While on mine ear it rings, 

 Through the deep caves of thought I hear a voice that sings: 



Build thee more stately mansions, my soul, 



As the swift seasons roll! 



Leave thy low-vaulted past! 

 Let each new temple, nobler than the last, 

 Shut thee from heaven, with a dome more vast; 



Till thou at length art free, 

 Leaving thine outgrown shell, by life's unresting sea! 



