The _Crotali_ do not gain a single joint only to the rattle annually, as is generally supposed. They gain more than one each year, the exact number being probably regulated in a great measure by the quantity of nourishment the animal has received. Rattle-snakes in Peale's Museum have been observed to produce 3 or 4 in a year, and to lose as many from the extremity during the same time. Hence it is obvious, that the growth of these curious appendages is irregular, and that the age of an individual cannot be determined from their number. Mr. Rubens Peale informed me, that a female of _Crotalus horridus_, Beauv. _durissus_, Daud. which lived in his Museum more than fourteen years, had eleven joints to her rattle when first in his possession; that several joints were acquired and lost annually, and that at her death, which occurred last year, she had the same number as when brought to the Museum; she had, however, during that time received an accession of four inches to her length. Her death was occasioned by an abortion. The _C. adamanteus_, Beauvois. _Rhombifer_, Daud. is by much the largest of our North American serpents, and doubtless is the species which Catesby saw a specimen of, eight feet long. _Crotalus miliarius_ varies in some characters from those laid down by authors. A specimen within my view has five dorsal series, of alternate, irregularly orbicular black spots, those of the intermediate series are obsolete, and slightly connected across the back, those of the vertebral series have not red centres, and are edged with a white line; the ventral spots are disposed adventitiously, so as not to be traced into longitudinal series; they are large, black, irregularly orbicular, and occupy about one half of the surface, which is white. Ventral plates 140; subcaudal, 33, of which the six terminal ones are bifid. Joints of the rattle with but one transverse contraction on the middle of each, besides the terminal contraction. Total length 1 foot 4¼ inches, tail two inches. It appears to be more vindictive than the two species before mentioned. The individual here noticed we encountered in East Florida; he struck at Mr. W. Maclure and myself successively as we passed by him, without any previous intimation of his presence, owing to the inaudible smallness of his rattle, and its having but three joints; he was killed by Mr. T. Peale, (whom we preceded) while preparing for another assault. This incident is noted as a contrast to the anecdote of the _Coluber heterodon_. _Salamandra alleganiensis_, Daud. appears to be synonymous with _S. gigantea_ of Dr. Barton. It was first described by Mr. Latreille in Deterv. Ed. of Buffon, tom. 11. The name _alleganiensis_, although defective, as it indicates no character, has however the unalienable right of priority. _Salamandra subviolacea_, Barton. This name has been rejected by Mr. Daudin, and substituted by that of _venenosa_, I do not know for what reason, as none is assigned.