316 E. T. Neidon—Pre-Glacial Mammalia. 



great extent bridge over tlie intervals between these, being looked 

 upim as varieties of one or other of them. 



To Elephas antiqiius are referred those comparatively narrow- 

 crowned molars, with wide plates of enamel more or less enlarged 

 in the middle, the enamel of which is thick and much crenulated. 

 This typical form occupies as it were a central position in the 

 species, and variation takes place in two directions. In the first the 

 enamel plates expand from before backwards, and when the tooth is 

 much worn, especially when worn very obliquely, the spaces are so 

 "wide as to resemble much the Loxodon type of tooth. This form 

 was referred by Dr. Falconer to E. priscus, but he afterwards came 

 to regard it as an extreme variety of E. antiquus. The second or 

 "broad-crowned" variety has the plates of enamel flattened and 

 nearer together, the enamel also in some cases being thinner and 

 less crenulated. The extreme examples of this variety approach so 

 near to those molars which are said to be the " Forest Bed " repre- 

 sentatives of the Mammoth that it is not always clear to which they 

 should be referred. In fact, there is every gradation of form between 

 the two species. 



To the species E. meridionalis are referred those massive molars 

 which are characterized by having very low crowns in proportion to 

 their great width, the enamel plates thick and widely separated, and 

 the enamel itself very thick and smooth, with little or no crenulation. 

 "Varieties of this form seem to connect the species with E. antiquus. 

 Mr. Gunn is of opinion that certain of these varieties, between the 

 three species above mentioned, should be elevated to the rank of 

 species, and he has proposed the names of E. leptodon and E. giganteus 

 for two of them. At present, however, these species have not been 

 defined, and Dr. Leith Adams, after long study, thinks it best to 

 look upon them merely as varieties. With the opinion of the latter 

 gentleman 1 feel constrained to agree, and to acknowledge with him 

 only three species oi Ehplias in the "Forest Bed," namely, E. antiquus, 

 E. meridionalis, and E. primigenius. At the same time it should be 

 remembered that the latter species is represented by a somewhat 

 extreme form which may eventually have to be regarded as distinct. 



Cetacea. 



JBalcenoptera? — Some very large Cetacean vertebrse from the 

 " Forest Bed " at Muudesley and Bacton are preserved in Mr. Gunn's 

 Collection at the Norwich Museum. Sir C. Lyell referred to these 

 in 1H63, as repi-esentatives oi Balccnoptera (Antiquity of Man, p. 216), 

 and Mr. Gunn, in 1864, considered that they belonged to " two species 

 of Whales" (Geol. Norfolk). The centrum of the largest has a 

 diameter of about 15 inches. It is not easy to say to which of the 

 larger whales these vertebree belong, but on the whole it seems most 

 probable that they belong to the largest form, namely, the Fin 

 Whales or Balcenoptera, and with some doubt it will be best to place 

 them in this genus without attempting any closer determination. 



Monodon monocems. — The earliest notice of the occurrence of the 

 Narwhale in the " Forest Bed " is in Sir C. Lyell's Antiquity of 



