In the early part of the present century were Latreille, Shaw, Daudin, Oppel, Merrem, Wagler, Neuwied, Cuvier, and many others till we come to Gray, Fitzinger, and Dumeril, 1844. This last author, in his introduction to _Les serpents solenoglyphes, dit Thanatophides_, including the most deadly snakes, devotes several pages to the subject of the ‘pit,’ and why it had especially occupied the attention of those herpetologists who were endeavouring to improve the previously imperfect systems. Wagler in 1824 assigned the name _Bothrops_ (from βὀθρος, any hole, or pit, or hollow dug) to vipers with the pit that had only scales and no plates or shields on their head, separating these from the rattlesnakes and from those that have shields (see illus. p. 318). This nomenclature of Wagler’s did not commend itself to other herpetologists, and Fitzinger, in his _Systema Reptilium_, 1843, extending the group, retained the name for one of the five families into which he divided all the venomous snakes. Fitzinger’s fifth family, the _Bothrophides_, included some of the Indian pit vipers; but as some of these latter have shields on their head, they could not be admitted into Wagler’s group with scales only. As the present object is to demonstrate some of the perplexities of naturalists, and to arrive at the reason why so many snakes without the _crotalon_ are called _Crotalidæ_, we will quote Dumeril’s reasons, inviting the reader to picture to himself the interest with which new examples were brought home for investigation, and the obstacles presenting themselves to herpetologists, who find one feature claiming alliance to this snake, while another feature points an alliance to an entirely opposite one. So Dumeril shows us why some of the herpetologists wished to admit _every species that has the nasal fosse_ under the generic name _Bothrophidæ_, and others would have limited the term to a few, because the name does not suit them all equally well. ‘_Beaucoup d’autres serpents presentent aussi des enfoncements creusés sur la tête et sur le bord des lèvres._’ These depressions, called by Professor Owen ‘secreting follicles,’ may be easily distinguished on the upper lip of some of the larger constrictors. In the Reticulated python you can count these pits like deep dimples round the mouth. In the Diamond snake (_Morelia spilotes_) they are remarkably deep along the lower lip. Of those ‘follicles’ in the _Crotalidæ_ Dumeril writes: ‘_Les fossettes paraissent devoir être des organes particuliers dont l’usage ou la fonction n’est pas connu il est vraix, mais qui semble avoir quelque importance par leur position constante entre les orifices réels des narines et les yeux, at leur structure anatomique assez compliquée. À cause de la grande analogie qu’ils ont tous avec les serpents à sonnettes, nous avons preféré appeler ceux-ci les crotaliens._’[107]