484. 13R- C. I. rOKSTTlI MAJOR ON 



Titanomys-ieeih ; and that itiTs having been lost in tlie former genus by some means or 

 otber, the terminal cusp of m. 2 has become enlarged in compensation. "We have 

 numerous analogies for similar occuri-ences, but we have none for the ever-recurring 

 theories of fusion between tooth and tooth, which on closer examination always break 

 down. This notwithstanding, we shall still hear of them, since they yield the explanation 

 which lies nearest at hand. 



Again, although Prolagus presents in its molars, at least in the upper ones, more 

 primitive characters than Zagopsis and Lagomys, it cannot be considered to be the 

 direct ancestor of these ; for it cannot be surmised that a tooth— mTs — after having 

 been lost, reappears in a later genus. Hilgendorf regards m. 3 of Lepus as a recent 

 acquisition, for he terms it '' phylogenetisch der jiingste (Zahn) " * ; presumably for 

 the same reason for which he considers tlic maximum of enamel-plication observed by 

 him in upper incisors (of ^' Lepus mexicanus") to l)e "phylogenetisch ein Extrem " t, 

 because there is no trace of it " bei den fossilen Leporiden-Gattungen {Mi/olagus)." 

 There is no good reason for considering the Miocene Prolagus {Ili/olagus) in the 

 ancestral line of Lepus, simply because no true Leporida? have been found in the 

 European Miocene ; nor in inferring from the various primitive characters of P;'oZ«(7?<s 

 that the absence of m. 3 is a primitive character as well. Besides, Hilgendorf does not 

 take into consideration the fact that Lagop)sis and Titanomys, both of which are contem- 

 poraneous with and even partly {T. visenoviensis) older than Pfolagus, possess a m. 3. 

 I presume that, for similar reasons, Hilgendorf would consider the m- 3 of Le^ms a recent 

 acquisition also ; and here we must remember tliat the Oligocene Pala'olagus has 

 both m. 3 and m. 3. 



Noack describes the last lower molar of young Lepus saxaUlis as composed of two 

 antero-posteriorly placed cusps, which seem (" scheinbar ") to be separate, but at any rate 

 (" jedenfalls ") are only loosely connected, which makes it doiibtf ul whether they ever 

 coalesce to form a compact tooth. This conformation of m. 3 is in the author's opinion a 

 sufficient justification for the folloAving generalization: "Jedenfalls ist im Unterkiefer 

 von L. saxatilis noch die Tendenz zu 6 Backenzahnen vorhaudcn." | Why not, while we 

 are at it, towards eight ? — since it is stated immediately afterwards that the same 

 partitioning of the two lobes is also visible in two of the anterior molars. The 



* Sitzungsber. d. Ges. natiirf. Freundo Berlin, Sitzung v. 1.5. Januar 1884, ]>. 23. 



t Op. cit. p. 20. 



+ Th. Noack, " Neue Beitriige zur Kenntniss d. Siiugethier-Fauna von Ostat'rika," Zool. Jahrb. Abth. f. 

 Syst. etc. vii. p. 54.5 (1693). The writer of this pamphlet has examined numerous dentitions of fostal and young 

 Habbits, and " -i. vulgaris" (meaning L. eiiropaits), and finds among other things in their cheek-teeth cusjjs which 

 are absent in the adult. So far, good. Apart from this, his descriptions and generalizations show on almost 

 every line that he has approached this difficult subject without sufficient scientific training. Hilgendorf's short 

 sentence of 1865 : " Die oberen Backzahne junger Hasen sind mit einer halbmondfurmigen Schmelzrijhre verschen, 

 wodurch ein Ubcrgang zu dem fossilen Mi/olat/us gebildet wird,"' — is of infinitely higher scientific value than the 

 •la^es filled with laborious descriptions in the paper quoted. If the author had taken Hilgendorf's words as a 

 starting-point and a guide in the investigation of upper leporine cheek-teeth, he might have been able to 

 do some useful work. He knows about tritubercular teeth ; he also seems to be aware that on ojie occasion 

 the molars of lagomorphous Rodents have been compared with those of diprotodont Marsupials, and that 



