370 MESSRS. ST. G. MIVAKT AND B. CLARKE 



12. Exhibits a vertical view of part of the edge of the above slab of Chwtetes 



hyperboreus, showing the comparative tenuity of the expansion. About 

 nat. size. 



13. A transparent vertical section of ChcBtetes hyperboreus, magnified 7 



diameters. 



14. A horizontal section of the same coral, X 7 diam. 



16. The surface, slightly weathered, of a piece of Pachypora lamellicornis, 

 Lindstrom. From the Wenlock (Upper Silurian), Gotland. Drawn 

 of nat. size from a specimen in the cabinet of Prof. Nicholson. 



16. A section in the plane of the frond of part of the same specimen of P. 



lamellicornis, rubbed down and viewed by transmitted light, X 4 diam. 

 Owing to the undulations of the specimen, the section cuts across the 

 corallites obliquely. 



17. A section at right angles to the plane of the frond of the same, mag- 



nified 4 diam. 



18. A superficial view of the surface of a fragment of Pachyjpora {Alveolites) 



Fischeri, Billings. From the Hamilton group, Middle Devonian, 

 Arkona, Ontario. Encrinital joints are adherent to the surface of the 

 specimen. Of nat. size and sketched from a specimen in Prof. 

 Nicholson's cabinet. 



19. A microscopical vertical section of fig. 18, X 7 diam. 



20. A segment of a transparent horizontal section of the same, also magnified 



7 diameters. 



21. Fachyjjora {Alveolites) frondosa, Nicholson. Vertical transparent section, 



X 6 diam. Specimen obtained from the Hamilton g^oup, Middle De- 

 vonian, Arkona, Ontario, and now in Prof, Nicholson's cabinet. 



22. A vertical section of the same specimen of P. frondosa, also X 6 diameters. 



On the Sacral Plexus and Sacral Vertebrae of Lizards. By St. 

 Geoe&e Miyaet, Sec. L.S., and the Eev. Egbert Clarke, 



■pi J Q 



[Eead May 3, 1877.J 

 (Abstract.) 

 The authors mention that of late it has been recognized that, in 

 any attempt to answer the question as to which vertebra of any 

 lower animal answers to the first sacral vertebra of Man, the ner- 

 vous no less than the osteological relations of the parts should be 

 carefullv investigated. And it has been considered that the 

 nervous rather than the osteological relations should be deemed 

 the more important : in fact it has been sometimes asserted that 

 the nerves must be taken as the fixed points, and that the bones 

 must rather have their homology decided by the nerves, than vice 

 versd. 



Should it be possible to show that in any group of reptiles, both 



