136 Dr. A. Giinther on two Snakes. 



garded as having a generic value ; but he still seemed to look 

 with favour on, and later he and his co-worker E. Desor, 

 and again still later Desor separately, made some use of, the 

 partitions. Alex, Agassiz, adopting his father's distinctions, 

 has separated off as a subgenus the forms in which the parti- 

 tions seemed to be better developed. These differences I have 

 shown in these observations to depend on age more than, 

 rather than as much as, on species ;. and the last reason for 

 separating Peronella (A. Ag.) from Laganum is hereby re- 

 moved. 



The real case would seem to be best and most truthfully 

 represented by allowing that, in the case of Laganidse, some 

 of what we call specific characters are by no means definitively 

 fixed. 





XVI. — Description of two Snakes from the c Challenger ' 



Collections, By Dr. A. Gunthek, F.R.S. &c. 



Among the Snakes collected by the naturalists of the c Chal- 

 lenger' Expedition there were two which are apparently 

 undescribed. They, with a number of others which were 

 desiderata in the British Museum, are now deposited in the 

 national collection. 



Tropidonotus dendrophiops. 



Habit slender; head resembling that of Dendrophis] eye 

 very large. Scales in seventeen rows, strongly keeled. Ven- 

 trals 157; anal divided; subcaudals 100. Anterior frontals 

 subtruncated in front, nearly as long as posterior. Loreal 

 large, somewhat longer than high. One praeocular, reaching 

 to the upper surface of the head, but not to the vertical. 

 Three narrow postoculars. Upper labials nine, the fourth, 

 fifth, and sixth of which enter the orbit, and are narrow on 

 account of the large size of the eye. Temporals irregular in 

 size and arrangement ; two are in contact with the post- 

 oculars. The maxillary teeth form one continuous series, and 



