In the second memoir of this series, which appeared in 1869, Flower treated in an exhaustive manner of the osteology of the sperm-whale, or cachalot. “The fine skeleton of a young male which he procured for the Museum of the Royal College of Surgeons,” writes Professor M’Intosh in his obituary notice of Sir William, “formed the basis of this important paper, and enabled him to add to and correct much which had been written on this subject. The description of its huge cranium as a large, pointed slipper, with a high heel-piece and the front trodden down, the hollow limited behind by the occipital crest, continued laterally into the elevated ridges of the broadly expanded maxillæ, which rose from the median line to the edge of the skull, instead of falling away, as in most Cetaceans, must be familiar to all students of the group. In this vast cavity lies the ‘head-matter,’ composed of almost pure spermaceti.” It was further demonstrated that the available evidence pointed to the existence of only a single species of true cachalot; the small adult jaws not unfrequently seen in collections being apparently those of females, which are known to be far inferior in size to the old bulls. It may be added, in connection with sperm-whales, that the abrupt termination of the muzzle, shown (in a somewhat modified degree) in the model of the old bull, set up under Sir William’s direction in the Whale Room at the Natural History Museum, has been said by certain modern naturalists to be incorrect. Inquiries instituted at the present writer’s suggestion at the New Bedford Cachalot-whaling Station have, however, proved that the abruptness is under-estimated rather than exaggerated in the restoration. This brief reference to the Whale Room at the museum, and Flower’s work in superintending the construction of models of several of the larger members of the group, must, it may be further added, suffice in this place, seeing that fuller mention of the subject has been already made in an earlier chapter. The third memoir of the series in the Zoological Society’s _Transactions_ treats of the Chinese white dolphin (_Delphinus_, or _Prodelphinus_, _sinensis_), and was published in 1872. In the following year appeared one on Risso’s dolphin, _Grampus griseus_, in which the author directed attention to certain variable markings always seen on the skin of this species. These, it has been subsequently shown, are produced by the claws in the suckers of the cuttlefish which forms the food of this species.