some time before it makes a second venture. I have seen a rattlesnake thus timidly advancing and recoiling three or four times before it has the courage to give the fatal stroke. Even after the bite it watches its victim with a steadiness in which terror is the strongest expression; and when the rat has remained motionless for a time, and the rattlesnake ventures near to investigate and make sure it is dead, one faint gasp or dying struggle will cause the reptile to dart back in excessive alarm, and wait again some minutes before venturing near. After long and patient observations, I am still doubtful whether stupidity or timidity predominates in viperine natures. Of the other well-known and formidable American _Crotalidæ_ is the ‘_Fer de lance_’ (_Trigonocephalus lanceolatus_) of the Antilles and Central America. This has also a pointed tail. The Jararaca of Gray (_Craspedocephalus Braziliensis_) is another, but without the point. Of the true rattlesnakes, Dumeril gave five genera in 1844, viz. _Crotalophorus_, _Crotalus_, _Caudisona_, _Urocrotalon_, and _Urosophus_. From the two species originally known, we see how they have gradually multiplied as the country has been more thoroughly explored. In 1860, Dr. Weir Mitchel affirmed that twenty species had been then described; probably the most recent ‘Reports’ or Bulletins will tell us of yet others. And these latter are exclusive of the non-rattle-bearing _Crotalidæ_. Dr. Mitchel’s experiments were with the northern species, chiefly _Cro. durissus_; and as a relief from this wearisome classification, some of his observations will be welcome. One very noteworthy result is that the Crotalus does occasionally produce a sound independently of the rattle. Not a prolonged hiss, or by any means so loud as the innocent snakes, but merely ‘the expiration of air from the lungs just before striking.’ I have never observed or heard this in our London rattlesnakes, but it no doubt is of the same character and degree of sound as that produced by the _Cerastes_ and the little _Echis_, and which more resembled a short, feeble, spitting sound. Still, as we are informed by Dumeril that rattlesnakes are ‘deprived of voice,’ it is interesting to know that, on the authority of Dr. Weir Mitchel, some slight sound, though not a regular hiss, does sometimes accompany the action of striking.