Dr. J. E. Holbrooke, in his _North American Herpetology_, published at New York in 1842, corroborates all Catesby further said regarding the fish-loving tastes of the ‘Thorn-tail’ snake, and which obtained for it the specific name _piscivorus_. It frequents damp and swampy places, and is never seen far from water. In the summer (during Catesby’s time), great numbers might be seen lying on the low boughs of trees overhanging a river, whence they would drop into the water and pursue the fish with great swiftness. Few fish exceed its velocity in swimming. _Cenchris_ or _Trigonocephalus piscivorus_ is the name by which American herpetologists now recognise it. It is becoming rare where formerly it abounded, but is still found in the wilder districts of the less settled States, and in the hot weather may be seen lying motionless on the low branches, and often so like a portion of the bough as not to be observed till the sudden plunge tells that a deadly snake was close at hand. It is a cannibal besides, and other snakes are afraid of it and give it a wide berth. The horny spine (which is a mere hardening and consolidation of the terminal scales) and another feature, namely the ‘pit’ in its cheeks, described in chap. xxi., prove it to be allied to the rattlesnake. It is therefore included among the _Crotalidæ_, of which more hereafter.[53] A number of the ‘Pit vipers’ and _Trigonocephali_ are furnished with hard-pointed tails, and when they vibrate them rapidly, as many snakes do under excitement, the rustling against the dead leaves produces a sound very similar to the sibilation of the true _Crotalus_ tail. [Illustration: Tail of _Lachesis mutus_ (exact size).] _Trigonocephalus contortrix_, the ‘Copper-head,’ is another of these. Also the renowned ‘Bushmaster’ of Guiana and Brazil (_Lachesis mutus_, or _Crotalus mutus_), of which latter Darwin wrote, confirming Cuvier’s reasons for making it a sub-genus of the rattlesnake:—‘I observed a fact which appears to me very curious, as showing how every character, even though it may be independent of structure, has a tendency to vary by slow degrees. The extremity of the tail of this snake is terminated by a horny point, which is slightly enlarged, and as the animal glides along, it constantly vibrates the last inch or so; and this part, striking against the dry grass and brushwood, produces a rattling noise which can be distinctly heard at the distance of six feet. As often as the animal was irritated or surprised, its tail was shaken, and its vibrations were extremely rapid. This _Trigonocephalus_ has, therefore, in some respects the structure of a viper with the habits of a rattlesnake.’