Terry — The Nasal Skeleton of Amblystoma punctatum. 119 



The ethmoidal bridge of Amblystoma is a transitional struc- 

 ture in the building up of the ethmoidal plate as is the case 

 in Salamandra; in Triton the bridge is permanent. The 

 formation of the nasal septum of Rana bears no resem- 

 blance to the process in Amblystoma where an arch is at 

 first made over the internasal room and later a strong com- 

 missure is formed between the nasal capsules. 



The Cornu trabeculae of Amblystoma supports at its end 

 the organ of Jacobson. (Compare Seydel, '95 p. 478, 

 and fig. 7). In Rana the horn takes part in the posterior 

 division of the floor of the inferior room ; in the anterior 

 part the floor is formed by new chondrification. A floor 

 for the anterior part of the nasal capsule seems to be the 

 rule for Amphibia ; what part the trabecular horn plays in its 

 formation is known in but a few cases. In Necturus and 

 Proteus which do not possess a Jacobson' s organ a nasal 

 capsular floor is not present. On the other hand a Jacobson's 

 organ is described by Seydel for Siren but according to 

 Wilder's ( '91 ) description of the capsule there appears to be no 

 floor; yet there is to be found in Wilder's figure on the ventral 

 sido of the anterior end of the nasal skeleton a peculiar '* in- 

 ferior process " which is described on P. 35 where it is also 

 stated that the R. ophthalmicus profundus is ensheathed by 

 cartilage. The foramen of exit for this nerve is at the 

 medial, ventral corner of the nasal capsule at its cephalic end. 

 The meaning of the trabecular horn cannot be told until 

 more is known of its early development and its later history. 



Among the later developments, the slender bridge connect- 

 ing the trabecular horn and Lamina cribrosa is interesting. 

 The nasal capsule of my stage V, closely resembles that of 

 the 12 cm. Siredon described and shown in fig. 7 of Seydel's 

 work ('95). In its connections with roof and floor and in its 

 relations to the Fenestra narina and nasal duct the little 

 bridge is comparable with that marked ** d " in Seydel's 

 figure. Through further chondrification a fenestrated side- 

 wall is formed for the nasal capsule as Winslow has shown 

 (fig. 12), and in the partition between the two lateral windows 

 I see the little bridge of my stage V. Bruner ('02) has 



