or common cross adder. In Denmark, Norway and Sweden, the snake is known as hugorm, hoggorm and huggorm, roughly translated as 'striking snake'. In Finland, it is known as kyykäärme or simply kyy, in Estonia it is known as rästik, while in Lithuania it is known as angis. In Poland the snake is called żmija zygzakowata, which translates as 'zigzag viper', due to the pattern on its back. Description Relatively thick-bodied, adults usually grow to in total length (including tail), with an average of . Maximum size varies by region. The largest, at over , are found in Scandinavia; specimens of have been observed there on two occasions. In France and Great Britain, the maximum size is . Mass ranges from to about . The head is fairly large and distinct and its sides are almost flat and vertical. The edge of the snout is usually raised into a low ridge. Seen from above, the rostral scale is not visible, or only just. Immediately behind the rostral, there are two (rarely one) small scales. Dorsally, there are usually five large plates: a squarish frontal (longer than wide, sometimes rectangular), two parietals (sometimes with a tiny scale between the frontal and the parietals), and two long and narrow supraoculars. The latter are large and distinct, each separated from the frontal by one to four small scales. The nostril is situated in a shallow depression within a large nasal scale. The eye is relatively large—equal in size or slightly larger than the nasal scale—but often smaller in females. Below the supraoculars are six to 13 (usually eight to 10) small circumorbital scales. The temporal scales are smooth (rarely weakly keeled). There are 10–12 sublabials and six to 10 (usually eight or 9) supralabials. Of the latter, the numbers 3 and 4 are the largest, while 4 and 5 (rarely 3 and 4) are separated from the eye by a single row of small scales (sometimes two rows in alpine specimens). Midbody there are 21 dorsal scales rows (rarely 19, 20, 22, or 23). These are strongly keeled scales, except for those bordering the ventral scales. These scales seem loosely attached to the skin and lower rows become increasingly wide; those closest to the ventral scales are twice as wide as the ones along the midline. The ventral scales number 132–150 in males and 132–158 in females. The anal plate is single. The