Dr. H. Falconer -ow tlie Fossil Mastodon of Britain, 233 



Here the ridge-formirla is anisomerous, and regulated by progressive 

 increments, as 8, 12, 16; the higher its numerical expression, the 

 greater the liability to vary, within certain limits dependent upon 

 the race, sex, and size of the individual ; the lower molars often 

 exhibiting an excess of plates over those in the upper molars. 



Reverting to the Mastodons, Dr. Falconer observed that the sub- 

 genera Trilophodon and Tetralophodon, as regards number of forms, 

 are of nearly equal value ; the former comprising seven, and the 

 latter six well-marked species. Each group is divisible into two 

 parallel subordinate groups. In the one series the ridges are broad, 

 transverse, more or less compressed into an edge ; with the inter- 

 mediate valleys open throughout and entirely uninterrupted by sub- 

 ordinate tubercles. These are represented in Trilophodon by Triloph. 

 ohioticus, and in Tetralophodon by Tetr. latidens. In the other 

 series the ridges are composed of blunt conical points, which are 

 fewer in number, flanked in front and behind by one or more 

 subordinate outlying tubercles, which disturb the transverse direction 

 of the ridges and block up the valleys. This series is represented by 

 Trilophodon angustidens and by Tetralophodon arvernensis. In both 

 subgenera the species with transverse compressed ridges may be 

 compared with Dinotherium, as regards their molar crowns ; and 

 the other series with Hippopotamus. 



The European fossil species oi Mastodon, according to the author, 

 are the following : — Trilophodon Borsoni, I. Hays, Tril. tapiroides, 

 Cuvier, Tril. angustidens, Cuvier {pro parte), Tril. pyrenaicus, Lartet 

 MS., Tetralophodon longirostris, Kaup, and Tetr. arvernensis, Croizet 

 and Jobert. With the exception of Triloph. Borsoni and Tetral. 

 arvernensis, which are of Pliocene age, the above-named species are 

 of Miocene age. 



Dr. Falconer proceeded to state that the remains of only one species 

 of Mastodon have hitherto been discovered in the British Isles. They 

 occur in what is called the Older Pliocene Red Crag, at Felixstow 

 and Sutton, in Suffolk, and in the Newer Pliocene Fluvio-marine or 

 Mammaliferous Crag at various localities near Norwich and in 

 Suffolk. After remarking that Professor Owen had referred the 

 teeth of the Crag Mastodon to M. angustidens, making M. longi- 

 rostris and M. arvernensis to be synonyms of this species (as 

 Cuvier had also done), Dr. Falconer gave in detail the history 

 of the discovery and publication of the true M. angustidens (Cuvier), 

 and of the M. arvernensis and M. longirostris. He then passed 

 in review the opinions and statements of these authors, as well as 

 of Blainville, Laurillard, Gervais, Pomel, Lartet, and Sismonda, on 

 these species, and on the specimens which these observers had 

 severally described, sometimes under additional specific names. 

 He then described the characteristic peculiarities both of the molars 

 and of the symphysis of the lower jaws in these three species ; 

 and showed that the molars from the Crag Mastodon were, like 

 those of Tetral. arvernensis, characterized by four-ridged molars, 

 with their conical points more or less alternating, and with their 

 valleys blocked up ; and that they essentially differed from the molars 



