26 IOWA STUDIES IN NATURAL HISTORY 
i1, Body scales smooth (i. e. without median keels). Body with 
broad dorsal blotches of red bordered with black and separated 
by bands of whitish or yellow. 
Lampropeltis triangulum syspila (Cope). 
i2. Body scales each with a median lengthwise keel. 
jt. Body scales in 27 to 33 rows; rostral plate conspicuously en- 
larged and partially separating the two scales behind it; pat- 
tern of many large spots................ Pituophis sayt (Schlegel). 
j2.. Body scales in 19 to 21 rows; rostral normal; pattern of 
lengthwise stripes. 
ki. Lateral stripe extending upon the fourth row of dorsal 
scales anteriorly (counting from the belly); scales in 21 
OW Bsr ses eee Thamnophis radix (Baird & Girard). 
k2, Lateral stripe not extending upon the fourth row of dor- 
sal scales anteriorly; dorsal scales in 19 rows...........-..------ 
Thamnophis sirtalis partetalis (Say). 
h2. Anal plate divided. 
l1. Dorsal scales keeled. 
mi. Rostral normal,—not enlarged and recurved; body slender. 
n1, Scales in 25 to 27 rows, only faintly keeled; pattern of 
large spots; size large......Hlaphe vulpina (Baird & Girard). 
n2, Seales in 15 to 17 rows, distinctly keeled; pattern not of 
large spots; size small. 
01. Scales in 17 rows; a single scale in front of the eye; 
belly - whitish.—.__.___..._.... Storerta dekayi (Holbrook). 
02. Seales in 15 rows; two small scales in front of the eye; 
belly, reddish Storeria occipito-maculata (Storer). 
m2. Rostral enlarged and recurved; body stout..........----c-scessees-= 
Heterodon nasicus Baird & Girard. 
12. Dorsal scales smooth (not keeled). 
p1. Dorsal scales in 15 rows; bright green above, belly light, 
unspotted.—__- Liopeltis vernalis (Harlan). 
p2. Dorsal scales in 17 rows; ashy to brownish black above, bel- 
ly yellow or reddish with small black spots...............---..--.---- 
Diadophis punctatus arnyi (Kennicott). 
g?. Anterior fangs present in upper jaw; rattle on end of tail; large 
plates on top of head Sistrurus catenatus catenatus (Rafinesque). 
BIBLIOGRAPHY 
Carman, J. Ernest.—The Pleistocene Geology of Northwestern Iowa.— 
Iowa Geol. Surv., 26: 233-445. 1917. 
Shimek, B.—-The Plant Geography of the Lake Okoboji Region —Bull. 
Lab. Nat. Hist. Univ. Iowa 7, No 2: 3-90, pl. 1-8, map. 1915. 
Ruthven, A. G.—The Faunal Affinities of the Prairie Region of Central 
North America.—Amer. Nat. 42: 288-393. 1908. 
2 eS ee, —Contributions to the Herpetology of Iowa, II.— 
Proc. Iowa Acad. Sci. 17: 198-200, figs. 1-11. 1910. 
Aid ee ea ree —Contributions to the Herpetology of Iowa, II.— 
Proc. Iowa Acad. Sci. 19: 207. 1912. 
pS ES Vie eee ee —Contributions to the Herpetology of Iowa, III. 
—Occasional Papers, Mus. Zool. Univ. Mich. no. 66: 1-3. 1919. 
