702 PROFESSOR WILLIAMSON ON THE SCALES AND BONES OF FISHES. 
Fig. 29. Horizontal section of the ossified surface of the neural spine of the same 
fish. Magnified 25 diameters. 
Fig. 30. Enlarged view of one of the osseous plates of fig. 29. Magnified 160 dia- 
meters. 
Fig. 31. Vertical section of one of the same osseous plates with its subjacent cartilage. 
Magnified 125 diameters. 
Fig. 32. One of the small interspaces between the contiguous osseous plates, fig. 
29 d. Magnified 130 diameters. 
PLATE XXXI. 
Fig. 33. Vertico-transverse section of one of the vertebrae of Carchar'ias vulgaris, 
midway between the two terminal cones. Natural size. 
Fig. 34. Small portion of the internal structure of the same. Magnified 250 dia- 
meters. 
Fig. 35. Small portion of the margin of fig. 36 c. Magnified 200 diameters. 
Fig. 36. Vertical section of the vertebra of Carcharias vulgaris, parallel with the 
vertebral axis. Slightly enlarged. 
Fig. 37 . Longitudinal section of the carpal bone of a young Pike, {Esox lucius). 
Magnified 20 diameters. 
Fig. 38. Longitudinal section of the extremity of the opercular condyle of the epitym- 
panic bone of the Pike. Magnified 16 diameters. 
Fig. 39. Vertical section of the proximal half of one of the condyles of the same bone 
in a younger fish. Magnified 24 diameters. 
Fig. 40. Vertical section of the articular extremity of the opercular bone of a Pike. 
Magnified 16 diameters. 
Fig. 41. Vertical section across the centre of the vertebra of a Pike, at right angles 
to the vertebral axis. Magnified 8 diameters. 
Since the preceding memoir was written, I have had the opportunity of examining 
the scales of the Eel, to which my attention was directed by my friend Dr. Car- 
penter. I find that in them the calcareous portion consists of a single layer, of 
detached calcareous granules, which have not coalesced so as to form a continuous 
tissue. This is interesting, since it exhibits a rudimentary modification of the type, 
which becomes so much more fully developed in the scales of the higher osseous 
fishes. 
