OF THE RED CRAG. 



a? 



As to the character of interconfluence of the premaxillaries at the region of the pre- 

 nasal fossa, it may be permitted to doubt whether an intervening ossific production of the 

 prefrontals, as at i4, PL I, fig. 2, PI. IV, tig. 3, and in woodcut, fig. 13, 14, has not 

 been so interpreted. 



Of the second representative of ZipUopsis {Z. servatus) the author knows but a 

 single fragment of rostrum ' presque entier a sa pointe' (1. c, p. 629), and broken ofF in 

 front of the prenasal fossa ; it shows the same palatal portion of vomer as in Ziphius 

 Layardi. 



Rhinostodes, Bu Bus} — This genus is founded on a less compact or spongy texture 

 of the fossil bones forming the mid-part of a much mutilated rostrum. 



ZiPHiROSTRUM, V. Ben.- — In this genus the rostrum is straight, or bent slightly 

 upward at the point. The maxillaries are more or less thick. The premaxillaries 

 (' incisifs') are confluent along their inner borders at the mid-part of the rostrum, but 

 distinct at the point. The vomerine canal is open ; i. e. the premaxillaries are distinct 

 or apart at their upper borders, the interspace not being occupied by an ossified prefrontal 

 cartilage. 



It is well that the direction of the rostrum is not seized as a generic character. 

 Whether the degree of ossification of the prefrontal gristle be more entitled to serve as 

 such is questionable. In some Z'tphirostra the vomer appears as part of the palate, and, 

 as usual, " an pen en avant du point occupe par I'extremite anterieure des palatins" (loc. 

 cit., p. 624, Ziphirosirmn marginatum, Du B.) ; and " dans le tiers moyen de la longueur 

 de celui-ci" (ib., p. 623, in ZipJtirostruin Turninense). 



As to the confluence of the inner (mesial) borders of the premaxillaries, this, which 

 first affects their lower margins, is an affair of age and a matter of degree, in fossil 

 Ziphioids difficult to determine with any degree of certitude. 



Aporotus, Du Bus. — This genus^ has the same characters as ZipJiirostrum, save that 

 the inner borders of the premaxillaries in their rostral extent remain applied to one another 

 without ever (?) becoming confluent. 



1 "Rhinostodes Antwerpiensis, Du Bus. II n'existe au M usee qu'un seul fragment de tete de cet 

 animal; c'est la partie moyenne d'un rostre extremenient mutile." p. 629. — Recent Ziphii, as well as fossil 

 ones, exhibit degrees of difference in the density of the tissue of the bones forming the rostrum. The 

 prefrontal production appears to have been ossified in the portion of rostrum representing the genus 

 Rhinostodes, Du B. 



- " Genre Ziphirostrum, Van Beneden. Rostre droit ou legerement releve vers la pointe. Maxillaires 

 plus au moins epais. Incisifs sondes ensemble par leur bords internes, dans la partie moyenne du museau, 

 mais separe a la pointe. Canal vomerien ouvert," — " Sur differents Ziphiides nouveaux du crag d' An vers," 

 par M. le Vicomte Du Bus (' Bulletin de TAcademie Royale des Sciences de Belgique,' 2e serie, tome 

 XXV, 18G8). 



^ " Le genre Aporotus a les memes caracteres que le genre Ziphirostrum, sauf que les bords internes des 

 incisifs, dans leur partie rostrale, restent appliques I'un centre I'autre et ne sont jamais sondes ensemble." 

 Loc. cit., p. 626. 



