Osteology of Loxomma Allmanni. 57 



concavities of these undulations and zigzags correspond to 

 the concavities of the borders of the plica, and therefore to the 

 secondary pulp-cavities before mentioned. 



The granular layer accompanies everywhere on each side 

 the sinuosities of the central band and its processes, and holds 

 the same relation to the tubular dentine of the secondary 

 toothlets as it does to the same tissue of the toothlets of the 

 exterior of the tooth ; and it can anywhere be seen that the 

 dentinal tubules have a similar course through that layer to 

 the central band. 



On scrutinizing closely the pale central band of a plica 

 with a g-inch object-glass, the tubules of dentine are clearly 

 seen at its margins ; many of them end there, or perhaps 

 are cut off, whilst others (mostly, but not always or every- 

 where, colourless) are distinctly observed to cross over the 

 pale band and unite with those of the other side, either as 

 straight tubes, or forming with them a delicate and pale net- 

 work, resembling that of the granular layer, but devoid of its 

 colour. 



V. The other bones of Loxomma that have been picked up 

 are as follows : — eighteen separate centra of vertebra?, and 

 twenty others imbedded more or less in slabs of shale in 

 company with entire or fragmentary ribs ; twenty-four ribs, 

 of which a good many are nearly perfect, showing the head 

 and tubercle ; and seventeen bones of the extremities, one of 

 which is a humerus, the rest digital, large and small. All 

 these bones are well ossified, and their articular surfaces 

 mostly perfect. 



The centra of the vertebra? are commonly of considerable size, 

 alternately larger and smaller, strongly compacted, and have the 

 anterior and posterior surfaces concave, the former being less 

 so than the latter; several show no facets for the heads of 

 ribs. 



The vertebral canal, where it _ can be seen, is small. The 

 arches are therefore short, but strong, and unite above in 

 a broad and high, but thin, spinous process ; this is entire in 

 only one specimen, but nearly perfect in two or three others ; 

 it stands up straight, inclining neither forward nor backward. 

 All parts of the vertebra? are well ossified. 



The following are the measurements of the vertebra, a 

 dorsal, which is the most perfect, and is figured in Plate VI. 

 fig. 4 : — Length of the body -f^- inch, transverse diameter 1-^ 

 inch, vertical diameter l-^inch ; height of neural arch -pg-inch, 

 height of spinous process 2 inches, length of same from front 

 to back IyV inch, thickness -^ inch. The body is grooved 

 transversely, and has on each side of its upper and lower 



