See note [347], above.
E. A. Minchin, Proc. Zool. Soc. 1889, p. 583.
For good illustrations of this see Sir J. Dalyell, "Rare and Remarkable Animals of Scotland," vol. i. 1847, pll. 13, 14, 18, 19, 20.
Archiv. Mikr. Anat. xiii. 1877, p. 795.
Agassiz and Mayer, Mem. Mus. Comp. Zool. xxvi. 3, 1902, p. 153.