140 FAUNA ANTIQUA SIVALENSIS. 



potamus, and from tlie marked distinctions in the incisive 

 apparatus of the Hijjfo-potamus Sivalensis, we shall, perhaps, 

 be justified in at once establishing a new subgenus in this 

 genus of mammalia, fixing the subgeneric characters on the 

 incisive teeth. So marked a distinction in the form, number, 

 and character of the incisors, will, we imagine, admit of such 

 an arrangement, with every advantage to science, and in 

 taking this stej) we place the new subgenus in the following 

 position and order ^ : — 



Genus— HIPPOPOTAMUS. 



1st Subgenus — Hexaprotodon. 



1. Species — H. Sivalensis (Nobis). 



2. Species — H. dissimilis (Nob.). An Lie, vel infra, potius referendus ? 



2nd Subgenus — Tetraprotodon. 



1. Species — H. amphibins. Recent. 



2. Species — H. antiquus (Cuv.). Fossil. 



3. Species— ZT. minor (Cuv.). Fossil. 



4. Species — H. medius (Cuv.). Fossil. 



5. Sjiecies — //. minimus (Cuv.). Fossil. 



The specific characters of the first species of our new sub- 

 genus are as follows : — 



Genus— HIPPOPOTAMUS. 



Siibgenus — Hexaprotodon. 



Species — Sivalensis. 



Char. — H. dentibus primoribus utrinqize sex, subaequalibus ; la- 

 niariis diffbrmibus : superioribus nempe quoad sectionem transversaleni 

 renifonnibus : inferioribus pyriformibus ; cranio elongato ; oculo ad 

 medium caput fere attingente ; facie ad latera valde sinuata. 



Before closing this paper, we may make a few general re- 

 marks on the remains of this genus, which, with the exception 

 of the Mastodons and Elephants, are by far the most numerous. 



As may be imagined in such an extensive collection we 

 find the remains of animals of all ages, with teeth in every 

 variety and state of detrition ; from the young animal with 

 the complicated and trij)le cylindered milk tooth, to the old 

 and worn down molar without any mark of the trefoil, and 

 with a simple encircluag ridge of enamel. In the fossil skull 

 described as approaching adult (from which the measurements 

 noted as No. 1 have been taken) we have a beautiful exhibi- 

 tion of the teeth in that state when the animal has just lost 

 its last milk tooth, and the new molar or 'dent de remplacement' 

 is just showing itself in germ, whilst the last permanent molar, 



' See cmlea, page 21 ; also Synopsis of Hippopotami in vol. ii. — [Ed.] 



