A very remarkable variety (var. _cettii_, Gené) from Corsica and Sardinia (Plate II., second figure) is grey or olive above, with the black markings confluent into more or less regular annuli, which are nearly as wide as the spaces between them; these annuli are often broken up on the middle line of the back, and alternating; the collar is absent, or is transformed into the first annulus, and the upper surface of the head is more or less spotted or blotched with black. This pattern is most distinct in young and half-grown specimens; in large examples the annuli may break up into spots, disposed with great symmetry in transverse series. The belly is black, spotted with white. A specimen 20 inches long, from Bona, Algeria (Lataste collection), has the posterior half of the head, from between the eyes and behind the postocular shields, of an intense black, followed by the usual yellow and black collar; two light dots close together on the parietal shields. Some specimens are entirely or nearly entirely black. In the var. _picturatus_, Jan, from the Caucasus, the upper parts are sprinkled all over with light dots, and the yellow collar is present; the belly is grey, dotted with black, and with white spots on the sides. In others the body is black above, and checkered black and white beneath (var. _scutatus_, Pall.), or entirely black (var. _ater_, Eichw.). This melanism never appears until the second or third year of life, the young being marked like the typical form. Albinos have occasionally been met with, yellowish flesh-colour with reddish markings, and a white or yellow collar, the eye and the tongue red. Such an albino, from Horsted Keynes, Sussex, is preserved in the British Museum. A remarkable aberration, to be regarded as an imperfect albino, has been found in Dorsetshire, and described as uniform whitish, with a well-defined broad longitudinal central dorsal pale yellow-brown band. _Size._--May reach a length of 6 feet 8 inches. Such giants, females, known from Sardinia, Sicily, and Istria, are, however, very exceptional, individuals of this species seldom exceeding a length of 4 feet. The largest British specimen on record, from Wales, is stated to measure 5 feet 10 inches. Males rarely exceed 3 feet. _Monstrosity._--A dicephalous young, with the two well-formed heads side by side, is preserved in the British Museum, and several others have been described, one being reported to have lived for about a month. _PLATE II_ [Illustration: TROPIDONOTUS NATRIX _After Sordelli_] [Illustration: T. NATRIX, VAR. CETTII _After Sordelli_] [Illustration: T. NATRIX, VAR. PERSA]