BULLETINS OF THE Zoological Society of San Diego No. 16 A Key to the Snakes of the United States By C. B. PERKINS In Charge of Reptiles, Zoological Society of San Diego SAN DIEGO, CALIFORNIA JUNE 10, 1940 Digitized by the Internet Archive in 2017 with funding from IMLS LG-70-15-0138-15 https://archive.org/details/bulletinsofzoolo1619unse BOARD OF DIRECTORS AND COMMITTEES OF ZOOLOGICAL SOCIETY OF SAN DIEGO BOARD OF DIRECTORS Harry M. Wegeforth, M.D., President L. T. Olmstead, Vice-President Fred Kunzel, Secretary Frank C. Spaulding, Treasurer F. L. Annable C. L. Cotant W. C. Crandall Gordon Gray J. Waldo Malmberg T. M. Russell Mrs. Robert P. Scripps Robert J. Sullivan Mayor of San Diego President of Park Commission HONORARY VICE-PRESIDENTS G. Allan Hancock Fred E. Lewis EXECUTIVE COMMITTEE Mrs. Belle J. Benchley, Executive Secretary C. R. Schroeder, D.V.M., Louis Gill, Veterinary Pathologist Architect L. M. Klauber, A. T. Mercier, Consulting Curator of Reptiles Consulting Engineer HOSPITAL COMMITTEE Rawson J. Pickard, M.D., Chairman Howard A. Ball, M.D. Wesley C. Crandall Denis L. Fox, Ph.D. Hall G. Holder, M.D. George L. Kilgore, M.D. Eaton M. MacKay, M.D. Francis M. Smith, M.D. Earl P. Warren Claude E. ZoBell, Ph.D. EDUCATIONAL COMMITTEE Mrs. Lena P. Crouse, Chairman Robert D. Harwood Ph.D. Earl U. Homuth AQUARIUM COMMITTEE Gerald MacMullen, Chairman Captain R. H. Baker Bates Harper Lt. Comdr. D. P. Marvin, U.S.C.G., ret. Dr. Charles H. Townsend SPONSORS FOR ANIMAL COLLECTING G. Allan Hancock Osa Johnson Fred E. Lewis THE PURPOSE OF THE SOCIETY 1. To advance science and the scien- tific study of nature. 2. To foster and stimulate interests in the conservation of wild life. 3. To maintain a permanent Zoolog- ical Exhibit in San Diego. 4. To stimulate public interest in the building and the maintenance of a Zoological Hospital. 5. To provide for the delivery of lec- tures, the exhibition of pictures, and the publication of literature dealing with natural history and science. 6. To operate a society for the mu- tual benefit of its members for non-lucrative purposes. BULLETINS OF THE ZOOLOGICAL SOCIETY OF SAN DIEGO No. 16 A KEY TO THE SNAKES OF THE UNITED STATES by C. B. Perkins In charge of Reptiles Zoological Society of San Diego SAN DIEGO, CALIFORNIA JUNE 10, 1940 CONTENTS Introduction 5 A List of the Snakes of the United States 6 Use of Key 13 Generic Key 14 Key to Each Genus (Alphabetically Arranged) 21 Drawings Showing Scale Nomenclature 56 Glossary 58 Index 61 [FRYE & SMITH, LTD. - SAN DIEGO] Perkins: A Key to the Snakes of the United States 5 Introduction Any key to the snakes of the United States or any large area con- taining a great number of genera must, of necessity, be a compilation, as no single individual has worked on more than a few genera. Such is the case with the present key. The reason for its publication is to place in convenient form a key, as nearly up-to-date as possible, cov- ering all of the snakes in the United States. Blanchard’s A Key to the Snakes of the United States , Canada and Lower California, 1925, has been used as a foundation. Correct taxonomic arrangement has been abandoned for the sake of convenience. The keys to several genera were written by others, in which case the name of the author and publication data accompany this key. These keys have been adapted to the present key and cut down to in- clude only those snakes found in the United States. There is such a great deal of variation in scalation, color, and pat- tern, both geographically and individually, among snakes of the same subspecies, that an occasional error will be made, but it is believed that most specimens will be run down correctly. In questionable cases, location is often a very important factor. Mr. Norman C. Bilderback prepared the line drawings, including those showing Crotalus and Sistrurus, which originally appeared in Klauber’s Key to the Rattlesnakes. The lettering on the drawings was done by Mr. Leslie C. Kobler. I am deeply indebted to the following for the use of keys, advice, and criticism : Charles M. Bogert of the American Museum of Natural History; Dr. William M. Clay of the University of Louis- ville; Henry S. Fitch of the U. S. Biological Survey ; Dr. Eugene S. McCartney of the University of Michigan; Charles E. Shaw of San Diego; William H. Stickel of the University of Michigan. Especially am I grateful to Mr. L. M. Klauber, who gave generously of his time in reading the manuscript. Any errors, however, are mine. C. B. Perkins. 6 Bulletin 16 : Zoological Society of San Diego A List of the Snakes of the United States FAMILY Lcptotyphlopidae GENUS Leptotyphlops FAMILY Boidae dulcis dulcis dissectus humilis humilis cahuilae segregus atahcnsis GENUS Lichanura roseofusca roseofusca GENUS gracia Charina bottae FAMILY Colubridae GENUS Carphophis amoena amoena helenae GENUS vermis Abastor erythrogramm us GENUS Farancia abacura abacura reinwar dtii GENUS Diadophis amabilis amabilis modestus occidentalis pulchellus similis vandenburghi punctatus punctatus arnyi edwardsii stictogenys regalis regalis GENUS arizonae Rhadinaea flavilata GENUS Hcterodon contortrix contortrix browni nasicus nasicus kennerlyi simus Perkins: A Key to the Snakes of the United States FAMILY Colubridae (continued) GENUS Opheodrys GENUS aestivus vernal is Coluber constrictor constrictor flaviventris GENUS mormon priapus flagell um flagellum flavigularis f re nation lateralis piceus scmilincatus ta cn iat ns tacn iatus girardi ruthveni schotti Drymobius mar gar it if crus GENUS Dry mar chon GENUS corais couperi melanurus S aha d ora gra h a i n iac g ral i ami a e hexalepis virgultca GENUS Phyllorhynchus browni browni lucid us cl c curt at us nubil us GENUS perkinsi Elaphc bairdi chlorosoma guttata laeta obsolcta obsoleta con finis q uadrivi ttata q uadrivittata deckerti GENUS rosacea sub ocularis vulpina Arizona elegans elegans occidentalis 8 Bulletin 16: Zoological Society of San Diego FAMILY Colubridae (continued) GENLT S Pitu op his GENUS catenifer catenifer annectens deserticola deppei deppei lodingi melanoleucus mugitus ruthvcni sayi sayi affinis Lampropeltis alterna calligaster clapsoides elapsoides virginiana getulus getulus boy lii brooksi calif orniae florid ana holbrooki GENUS nigra splendida yumensis multicincta pyromelana rhomb omaculata triangnlum triangulum amaura annulata gentilis syspila Stilosoma extenuatum GENUS Cemophora coccinca GENUS Rhinocheilus lecontei GENUS Contia tenuis Perkins: A Key to the Snakes of the United States FAMILY Colubridae (continued) GENUS Sonora GENUS episcopa miniata miniata linearis occipitalis scmiann id at a semian nulata blanchardi gloydi taylori Ficimia cana streckeri GENUS Chilomcniscus cinctus GENUS Natrix cyclopion cyclopion florid ana erythrogaster erythrogaster transversa grahamii kirtlandii rhombifera rhombifcra rigid a septemvittata sipedon sipedon clarkii compressicauda con fl ucns fasciata insularum pictiventris pleuralis taxispilota GENUS Seminatrix pygaea GENUS Storeria dekayi occipitomaculata victa GENUS Haldca striatula valeriae valeriae elegans 10 Bulletin 16: Zoological Society of San Diego FAMILY Colubridae (continued) GENUS Liodytes GENUS alleni Thamnophis angustirostris butleri eques hammondii marcianus megalops ordinoides ordinoides atratus biscutatus couchii elegans hydrophila vagrans ■radix sauritus sauritus proximus sackenii sirtalis sirtalis concinnus inf emails parie tails pickeringii tetrataenia GENUS Tropidoclonion line at um GENUS Coniophanes imperial is imperialis GENUS Oxybelis micro phthalmus GENUS Leptodeira septentrionalis septentrionalis GENUS Hypsiglena ochrorhynchus GENUS Trimorphodon lyro phones vandenburghi vilkinsonii Perkins: A Key to the Snakes of the United States 11 FAMILY Colubridae (continued) GENUS Tantilla atriceps coronata coronata wagneri eiseni gracilis kirnia nigriceps utahcnsis wilcoxi FAMILY Elapidae GE NUS Micrurus fulfills fulvius barbouri tenere GENUS Micruroidcs euryxanthus FAMILY Crotalidae GENUS : Agkistrodon mokasen mokasen cupreus laticinctus pis civ or us GENUS S' istrurus catenatus catenatus tergeminus miliarius miliarius barbouri streckeri 12 Bulletin 16: Zoological Society of San Diego FAMILY Crotalidae ( continued ) GENUS Crotahis adamanteus atrox cerastes horridus horridus atricaudatus lepidus lepidus klauberi mitchellii pyrrhus stephensi molossus molossus ruber scutulatus scutulatus tigris triseriatus pricei viridis viridis abyssus decolor lutosus nuntius oreganus willardi Perkins: A Key to the Snakes of the United States 13 Use of Key This key must be started at the beginning unless the generic name of the snake in question is known. Start with No. 1, which gives two choices ; take the correct alternative and proceed to the number which is given at the right ; continue in the same manner until the generic name of the snake in question is given. A key to that genus will be found on the page whose number is given after the generic name. The keys to the various genera are arranged alphabetically starting at page 21. Where there is but one snake in a genus, its name and range will be found in its alphabetical position. The ranges are in parentheses below the name of the snake, and in some cases were taken from the Check List.* Line drawings with scale nomenclature will be found at page 56. Technical terms are defined in the glossary, page 58. * A Check List of North American Amphibians and Reptiles by Leonhard Stejneger and Thomas Barbour; fourth edition, 1939. 14 Bulletin 16: Zoological Society of San Diego Generic Key 1. Ventral scales same size as dorsal. . . Leptotyphlops . . . Page 39 Ventral scales larger than dorsal and elongated transversely 2 Small ventral scales Transverse ventral plates 2. Deep pit between nostril and eye 3 No pit 5 Pit below nostral-eye line 3. Rattle on end of tail 4 No rattle Agkistrodon . . .Page 21 Sistrurus Crotalus 4. Top of head with large plates, including a pair of large, symmetrical parietals in contact Sistrurus . . . Page 47 Perkins: A Key to the Snakes of the United States 15 Top of head with scales of varying size; parietals, if en- larged, not in contact, nor symmetrical . . Crotalus . . . Page 25 Chin-Shields No Chin-Shields 5. One or two pairs of enlarged, elongated chin-shields be- tween the lower labials Scales between lower labials all small 7 6 Charina Lichanura 6. A large plate on top of head between the supraoculars. Charina. . . Page 22 Small scales on top of head between the supraoculars. Lichanura . . . Page 40 16 Bulletin 16: Zoological Society of San Diego Keeled or rough scales Smooth — not keeled 8 25 7. Keels on some or all dorsal scales All scales smooth 8. Anal plate divided 9 Anal plate not divided 21 9. Rostral turned up and keeled above. . . . Heterodon . . .Page 34 Rostral normal 10 10. Loreal present 11 No loreal Storeria. . .Page 49 11. 2 internasals 14 1 internasal 12 12. 5 tipper labials; 6 lower labials; 17 scale rows. Haldea . . . Page 34 7 or 8 upper labials; 8 to 10 lower labials; 19 or 21 scale rows 13 13. 14. 15. 16. No preocular (loreal in contact with eye) ; ventrals more than 160 Farancia. . .Page 33 1 preocular ; ventrals less than 140 Liodytes . . . Page 40 1 or 2 preoculars No preoculars (loreal in contact with eye) 5 or 6 upper labials Haldea 7 upper labials Abastor 17 scale rows More than 17 scale rows 16 15 . Page 34 . Page 21 17 19 Perkins: A Key to the Snakes of the United States 17 17. More than 100 caudals 18 Less than 50 caudals Seminatrix. . .Page 47 18. 7 upper labials; 7 or 8 lower labials; dorsal color grass- green Opheodrys . . . Page 44 9 upper labials; 10 or 11 lower labials; dorsal color dark with a light spot on each scale Drymobius . . .Page 32 19. 3 postoculars Natrix . . .Page 41 2 postoculars 20 20. 19 or 23 scale rows ; scales strongly keeled. .Natrix . . . Page 41 25 to 33 scale rows; scales weakly keeled. . .Elaphe. . .Page 32 21. 29 or more scale rows Pituophis. . .Page 45 Less than 29 scale rows 22 22. No suboculars (upper labials in contact with eye) ; rostral normal 23 Suboculars present; rostral very large (with free lateral edges), separating internasals and in contact with pre- frontals Phyllorhync Jins . . .Page 44 23. 8 or more lower labials Thamnopkis . . .Page 51 Less than 8 lower labials 24 24. A double row of black belly spots. . Tropidoclonion . . . Page 55 No belly spots Haldea. . . Page 34 25. 26. Anal plate divided 33 Anal plate not divided 26 All or most caudals divided 27 Most caudals entire Rhino cheilus .. .Page 46 27. Pupil of eye round 29 Pupil elliptical 28 18 Bulletin 16: Zoological Society of San Diego 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. Suboculars present Phyllorhynchus . . .Page 44 No suboculars (upper labials in contact with eye) Trimorphodon . . .Page 55 Loreal present 30 No loreal Stilosoma. . . Page 49 Ventral surface light without markings 31 Ventral surface with at least some dark markings 32 6 upper labials ; 8 lower labials Cemophora. . . Page 22 8 upper labials ; 12 to 15 lower labials Arizona. . . Page 22 17 scale rows Drymarchon. . .Page 21 More than 17 scale rows Lampropeltis . . .Page 35 Less than 19 scale rows 34 19 or more scale rows 50 Loreal present 35 No loreal 45 1 or more preoculars 37 No preoculars ; loreal and prefrontal in contact with eye. ... 36 13 scale rows; nasal plate entire; 5 upper labials Carphophis . . .Page 22 More than 13 scale rows; nasal plate divided; 6 upper labials Haldea. . . Page 34 2 or 3 preoculars 38 1 preocular 41 Rostral normal 39 Rostral much enlarged with free lateral edges. Salvadora. . . Page 46 2 or 3 anterior temporals (usually) ; lower preocular very small, wedged between the adjacent upper labials. Coluber . . . Page 23 1 anterior temporal ; lower preocular not wedged between upper labials 40 Dorsal color not grass-green ; usually a ring on the neck ; nasal plate divided Diadophis . . . Page 29 Dorsal color grass-green ; no ring ; nasal plate entire. Ophcodrys . . .Page 44 17 scale rows 44 Less than 17 scale rows 42 Posterior chin-shields about as long as anterior chin-shields ; caudals more than 65 Oplieodrys . . .Page 44 Posterior chin-shields much shorter than anterior chin- shields ; caudals less than 65 43 Perkins : A Ivey to the Snakes of the United States 19 43. Ventral surface uniform light color, or, if any dark mark- ings, they are black rings that encircle the body ; no lateral light stripe on the 4th or 5th row of scales. Sonora. . . Page 48 Each ventral with a black anterior border ; usually a light stripe on the 4th or 5th row of scales. . . . Contia. . . Page 25 44. More than 60 caudals; a dark line from the rostral through the eye to the last upper labial ; 7 upper labials. Rhadinaea . . . Page 46 Less than 60 caudals; no dark line from the rostral to the last upper labial ; usually 8 upper labials. Seminatrix . . . Page 47 45. More than 13 scale rows 46 13 scale rows . . Page 23 46. 15 scale rows; nose normal. . . . 17 scale rows ; nose sharp 48 ....... 47 47. Rostral acute and turned up at tip ; tail short and thick. Ficimia. . . Page 33 Head long and nose sharp; tail long and slender (more than half the body) Oxybclis. . . Page 44 48. Coloration above uniform except near head; ventrals less than 190 Tantilla. . .Page 50 Coloration* consists of rings of black, yellow, and red ; ventrals more than 200 49 49. Only 1 pair of chin-shields, the anterior ones being replaced by the enlarged first pair of lower labials. Micruroidcs. . . Page 40 2 pairs of chin-shields Micrurus . . . Page 40 50. 1 or more preoculars 51 No preoculars (loreal in contact with eye) 53 51. Pupil of eye round Pupil elliptical 52 54 * Gloyd in Herpetologica Vol. 1, No. 5, 1938, records the capture of a melanistic specimen of Micrurus at Victoria, Texas. 20 Bulletin 16: Zoological Society of San Diego 52. 25 to 33 scale rows Elaphc . . .Page 32 19 scale rows C onio phanes .. .Page 25 53. Longitudinal stripes present A bast or . . . Page 21 No stripes Farancia . . . Page 33 54. 1 loreal ; 2 postoculars ; 1 anterior temporal ; 8 upper labials . . 55 2 or more loreals ; 3 or 4 postoculars ; 2 or 3 anterior tempo- rals ; usually 9 or more upper labials. Trimorphodon . . . Page 55 55. Dorsal pattern consists of small blotches with one or two series of smaller alternating spots on the sides ; one large dark blotch on each side of neck . . . . Hypsiglena. . .Page 35 Dorsal pattern consists of 22 to 26 large blotches with no alternating lateral spots Leptodeira. . .Page 39 Perkins: A Key to the Snakes of the United States 21 Genus Abastor Abastor erythrogrammus (Latreille) Rainbow snake. (Charles County, Maryland, southward to Florida and Alabama.) Genus Agkistrodon 1. Loreal present; no post-parietals ; upper labials not in con- tact with eye ; scale rows usually 23 Copperhead .... 2 No loreal; a pair of post-parietals; upper labials in contact with eye; scale rows usually 25 Water moccasin, Cotton mouth Agkistrodon piscivorus (Lacepede) (Dismal Swamp, Virginia to Florida and the Gulf States, and Arkansas to Illinois.) Very little constriction Spool-shaped Hour-glass-shaped 2. Dark dorsal cross-bands show very little constriction ; cross- bands 4 to 8 scales wide at the midline. Agkistrodon mokasen laticinctns Gloyd and Conant (Western and central Texas, western and central Okla- homa, north to Cowley County, Kansas.) Dark dorsal cross-bands show considerable constriction at the midline 3 3. Dark cross-bands are spool-shaped and 3 to 5 scales wide midline Agkistrodon mokasen cupreus (Rafinesque) (Eastern Oklahoma and eastern Kansas; parts of Arkan- sas and Missouri, north to Central Illinois, central Indiana and parts of Ohio, Pennsylvania and New York; Ap- palachian highlands, from the Tennessee River and north- eastern Alabama, to eastern Massachusetts.) Bands are hour-glass-shaped and 2 or 3 scales wide at midline Agkistrodon mokasen mokasen Beauvois (Atlantic coastal plain and lower Piedmont areas of Georgia and the Carolinas, exclusive of peninsular Florida.) 22 Bulletin 16: Zoological Society of San Diego Genus Arizona 1. 29 or 31 scale rows; squarish dorsal blotches, usually less than 56 ; lateral blotches distinct and roundish. Arizona elegans elegans Kennicott (Southwestern Kansas, southward through central Texas, westward to southeastern Arizona.) 27 scale rows (seldom 29) ; narrow dorsal blotches, usually more than 56 ; lateral blotches indistinct and narrow. Arizona elegans occidentalis Blanchard (Arizona, extreme southwestern Utah, southern Nevada, southern California and Lower California.) Genus Carphophis * 1. Color above generally brown; light color of belly extending to 1st or 2nd row of scales 2 Color above generally gray or black ; light color extending to 3rd scale row Carphophis amoena vermis (Kennicott) (Southern Iowa, southeastern Nebraska; eastern Kansas, Oklahoma and Texas; Missouri, Arkansas, Louisiana.) 2. Internasals and prefrontals usually separate. Carphophis amoena amoena (Say) (Connecticut to New York, south to central Florida, and west into the Appalachian Mountains.) Internasals and prefrontals usually united forming two large shields Carphophis amoena helenae (Kennicott) (Central Illinois south to Mississippi, east to north- western Alabama, the Tennessee Valley to eastern Ten- nessee, West Virginia and eastern Ohio.) Genus Cemophora Cemophora coccinea (Blumenbach) (Southern New Jersey to Alabama, Louisiana, Oklahoma and Florida.) Genus Char in a Charina hottae (Blainville) Rubber snake. (Humid districts of California south to the San Jacinto Mountains, Nevada, Idaho, Oregon and Washington, east to Montana, Wyoming and Utah.) * Snakes of this genus are commonly called Worm snakes. Perkins: A Key to the Snakes of the United States 23 Genus Chilomeniscus Chilomeniscus cinctns Cope. (Central and southwestern Arizona, to northwestern Mexico and central Lower California. One specimen each from Inyo County and Ft. Yuma, California.) Genus Coluber * 1. Scale rows at posterior end of body 15 (scale formula 17-15 or 15-15) 2 Scale rows at posterior end of body 13 or 11 (scale formula 17-13. 15-13, or 15-11) 5 2. Dorsal surface black or very dark gray ; belly dark gray ; caudals average 106. (Juveniles are blotched; under sur- face of lower jaw not marked with spots.) 3 Dorsal surface not black or very dark gray ; belly light bluish, greenish, or yellow; caudals usually less than 100 4 3. Some of the proximal spines of the hemipenes much en- larged into basal hooks. Coluber constrictor priapus Dunn and Woodf (Florida.) Proximal spines of hemipenes not enlarged into basal hooks. Coluber constrictor constrictor Linnef (Eastern United States, west to central Indiana, thence southwest through southern Illinois and eastern parts of Missouri, Arkansas, and Texas.) 4. 7 upper labials ; caudals usually less than 85 ; color above blue-gray or bluish. (Juveniles are blotched; under sur- face of lower jaw not marked with spots.) Coluber constrictor flaviventris Say (From Rocky Mountains east through Texas, western Arkansas, Missouri and Michigan, and northern parts of Illinois, Indiana and Ohio.) Upper labials usually 8 ; caudals usually more than 85 ; color above olive-brown, greenish, or blue-gray. (Juveniles are blotched; under surface of lower jaw not marked with spots) ..Coluber constrictor mormon Baird and Girard (California. Oregon, Washington, Montana, Idaho, Nevada and LYah.) 5. 15 scale rows 6 17 scale rows 9 6. Head plates with light edges 8 Head unicolor 7 * Snakes of this genus are commonly called Racers and Whip snakes, f If unable to use this internal diagonistic characteristic, separate these two subspecies by their ranges. 24 Bulletin 16: Zoological Society of San Diego 7. 2 to 4 dark and 2 light lateral stripes. Coluber taeniatus schotti (Baird and Girard) (Southern Texas and northeastern Mexico.) One or no light lateral stripe. Coluber taeniatus ruthveni (Ortenburger) (Southern Texas and Tamaulipas, Mexico.) 8. One or more light cross-bands just behind head or on neck and body . . . .Coluber taeniatus girardi Stejneger and Barbour (Central and western Texas southward to Zacatecas, Mexico.) No light cross-bands just behind head or on neck and body. Coluber taeniatus taeniatus (Hallo well) (Southeastern Oregon, southern Idaho, Nevada and Utah, southward to western Texas, New Mexico, Arizona, and California east of the Sierra Nevada.) 9. Distinct longitudinal stripes present 10 No distinct longitudinal stripes 11 10. 2 or 3 light lateral stripes anteriorly, not continued to the tail Coluber semiline atus (Cope) (Central and southeastern Arizona, extreme southwestern New Mexico, and south into Sonora.) One light lateral stripe, continuing to the tail. Coluber lateralis (Hallowed) (California and Lower California.) 11. Entire dorsal surface of body and tail black. (Juvenile col- oration unknown) Coluber piceus (Cope) (Southeastern Arizona and Lower California, just enter- ing extreme southern San Diego County, California.) Entire dorsal surface not black 12 12. Black or dark brown cross-bands across the neck or anterior fifth of body 14 No such black or dark brown cross-bands 13 13. Head and anterior portion of body very dark brown, grad- ually becoming much lighter posteriorly. Coluber flagellum flagellum Shaw (North Carolina to Florida, westward to eastern Texas and central Kansas.) Anterior portion of body not darker than posterior. Coluber flagellum flavigularis (Hallowed) (Western Kansas, southeastern Colorado south to central Mexico.) 14. A distinct horizontal white stripe, bordered by black, through loreal. (Juveniles are blotched: under surface of lower jaw spotted.) Coluber flagellum frenatum (Stejneger) Perkins: A Key to the Snakes of the United States 25 (Central and southern California, Lower California, Ne- vada, Utah, Arizona, western New Mexico, and Sonora to Sinaloa, Mexico.) No distinct horizontal white stripe through loreal 15 15. Dark brown cross-bands on neck separated by 1 or 2 scales of lighter brown ; most of last upper labial cream color — - Juvenile Coluber flagellum flagellum Shaw (North Carolina to Florida, westward to eastern Texas and central Kansas.) Dark brown cross-bands on neck separated by 3 or more scales of lighter brown ; all but anterior lower corner of last upper labial brown — Juvenile. Coluber flagellum flavigularis (Hallowed) (Western Kansas, southeastern Colorado south to central Mexico.) Genus C onio phones Conio phones imperialis imperialis (Baird) (Southern Texas to Vera Cruz, Mexico.) Genus Contia Contia tenuis (Baird and Girard) (Puget Sound to south central California.) Genus Crotalus* 1. Outer edges of supraoculars extended into raised and flexible hornlike processes distinctly pointed at the tip — Sidewinder Crotalus cerastes Hallowed (Deserts of the southwestern United States and north- western Mexico.) Outer edges of supraoculars not extended into raised and flexible hornlike processes 2 2. Tip of snout and canthus rostralis raised into a sharp ridge, by bending up of the outer edges of internasals and can- thals ; rostral and mental marked vertically by a narrow, light line on a red-brown ground Crotalus willardi Meek (Southern Arizona to Zacatecas, Mexico.) Tip of snout and canthus rostralis not raised into a sharp ridge; no central light line on rostral and mental 3 * Adapted from L. M. Klauber, A Key to the Rattlesnakes with Summary of Characteristics; Trans. S. D. Soc. Nat. Hist., Vol. 8, No. 20, 1936. 26 Bulletin 16: Zoological Society of San Diego 3. Upper preocular split vertically, the anterior section being- higher than the posterior and curved over the canthus rostralis in front of the supraocular ; prenasal curved under the postnasal ; usually a dorsal pattern of widely separated crossbars 4 Upper preocular not split vertically; or, if split, the anterior section not conspicuously higher than the posterior and not curved over the canthus rostralis in front of the supra- ocular ; prenasal not curved under the postnasal ; the pat- tern not of widely separated crossbars or rings 5 4. A dark stripe passing backward from the eye to the angle of the mouth; dorsal pattern of crossbars often not strongly differentiated from the ground color; ventral surface mottled Crotalus lepidus lepidus (Kennicott) (West Texas south to northern San Luis Potosi, Mexico.) No dark postocular stripe ; dorsal pattern of crossbars sharp- ly contrasting with the ground color ; ventral surface punctated Crotalus lepidus klaubcri Gloyd (Mountains of southern Arizona, Southern New Mexico, and extreme west Texas south to Jalisco, Mexico.) 5. Prenasals in contact with rostral; upper preocular not di- vided, or if divided the loreal conspicuously longer than high 6 Prenasals usually separated from the rostral by small scales or granules ; upper preoculars often divided, horizontally, vertically, or both Crotalus niitchellii pyrrhus (Cope) (Southern California, southern Nevada, western Arizona, and northern Lower California.) 6. Tail of alternating black, and light ash-gray rings, both colors being in sharp contrast with the posterior body color, which may be gray, dark-gray, cream, pink, red, red-brown, or olive-brown 7 Tail not of alternating black, and light ash-grav rings in strong color-contrast to the body color immediately an- terior to the tail 9 7. Dark and light tail rings of approximately equal width ; postocular light stripe, if present, intersects the upper labials from 1 to 3 scales anterior to the angle of the mouth ; minimum scales between supraoculars 3 or more ; no defi- nite line of demarcation between the scales in the frontal and prefrontal areas; proximal rattle black 8 Dark tail rings narrower than light ; postocular light stripe, if present, passes backward above the angle of the mouth; minimum scales between the supraoculars rarely more than 2 ; a definite division line or suture between the scales in the Perkins: A Ivey to the Snakes of the United States 27 frontal and prefrontal areas ; lower half of proximal rattle light in color ... .Crotalus scutulatus scutulatus (Ivennicott) (Southeastern California to west Texas, and south to the central Mexican plateau.) 8. hirst lower labials usually not divided transversely; general color cream, buff, gray, or gray-brown (sometimes pink or red in central Arizona or New Mexico) ; dark punctations conspicuous in marking Crotalus air ox Baird and Girard (Arkansas to southeastern California and south to San Luis Potosi, Mexico. Accidentally introduced in Vernon County, Wisconsin.) First lower labials usually divided transversely; general color pink, red, brick-red, or red-brown ; dark punctations weak- ly in evidence or absent from markings. . . Crotalus ruber Cope (Coastal southern California, and northern and central Lower California.) 9. Two internasals 15 More than two internasals in contact with rostral, regard- less of size or position 10 10. Light postocular stripe 1 or 1 1/2 scales wide and clearly out- lined ; body blotches commonly subrectangular, with even edges and usually with a narrow light border 11 Light postocular stripe 2 or more scales wide, often indefinite or absent ; body blotches, if in evidence, commonly dia- monds, or ellipses, or if rectangles, with edges rough or serrated, and often without narrow light borders 12 11. Color usually green or olive-green ; less often olive-brown or brown ; scale-rows 27 or 25 ; dorsal scale rows at the center of the tail 13 or more; adult size exceeding 850 mm. Crotalus viridis viridis (Rafinesque) (Western Great Plains from Alberta and Saskatchewan to extreme northern Mexico.) Color pink, red, or red-brown ; scale rows 25 or 23 ; dorsal scales at the center of the tail 12 or less; adult size rarely exceeding 650 mm Crotalus viridis nuntius Klauber (Northeastern Arizona.) 12. Color straw, cream, or yellow; blotches often only faintly in evidence or obsolete in adults ; adult size smaller, usually under 650 mm Crotalus viridis decolor Klauber (Eastern LTah and western Colorado.) Color darker, not straw, cream, or yellow ; adult size larger, over 650 mm 13 13. Adult color vermilion or salmon; body blotches tending to- ward obsolescence in adults.. .Crotalus viridis abyssus Klauber (Grand Canyon of Arizona.) 28 Bulletin 16: Zoological Society of San Diego Adult color other than vermilion or salmon ; body blotches in evidence, or body black 14 14. Ground color lighter, usually buff or drab ; body blotches occupy less or but little more longitudinal space than inter- spaces ; secondary series of lateral blotches little in evi- dence; a pattern of dark-brown dorsal blotches (often with light centers) on a buff or drab ground color. Crotalus viridis lutosus Klauber (The Great Basin between the Rockies and the Sierra Nevada.) Ground color darker, usually dark-gray, olive, brown, or black; dark-brown or black dorsal blotches (usually dia- monds or hexagons) occupying considerably more longi- tudinal space than the interspaces ; a secondary series of lateral blotches conspicuously in evidence. Some mountain specimens nearly uniform black, only patches of yellow scales representing the interspaces on the mid-dorsal line. Crotalus viridis oreganus Holbrook (Pacific Coast from British Columbia to central Lower California. Also mountains of Arizona and extreme west central New Mexico.) 15. A vertical light line on the posterior edge of the prenasals and first upper labials Crotalus adamanteus Beauvois (Coastal plains of the southeastern states.) No vertical light line on the posterior edge of the prenasals and first upper labials 16 16. Supraoculars pitted, sutured, or with outer edges broken. Crotalus mitchellii stephensi Klauber (Southern Nevada and east-central California.) Supraoculars not pitted, sutured, nor with broken outer edges 17 17. Head larger; head length contained less than 25 times in adult body length ; proximal rattle width contained in head length more than 2J4 times 18 Head notably small for a rattlesnake ; head length in adults contained in body length (over-all) 25 times, or more; proximal rattle width contained in head length less than 254 times Crotalus tigris Kennicott (Southern Arizona, and northern and central Sonora, Mexico.) 18. Usually a definite division between the scales in the frontal and the prefrontal areas; scales in the anterior part of frontal area larger than those behind; anterior body pat- tern not in chevron-shaped bands or not all black 20 Perkins: A Key to the Snakes of the United States 29 No definite division or continuous suture between the scales in the frontal and the prefrontal areas; scales in the an- terior part of frontal area not conspicuously larger than those behind ; normal pattern a series of chevron-shaped crossbands sometimes broken, or with the body all black. . 19 19. Dorsal scale rows usually 23 ; postocular dark stripe indis- tinct ; no middorsal reddish-brown stripe evident anter- iorly; sometimes entirely black. Crotalus horridus horridus Linne (Eastern United States, Maine to Oklahoma.) Dorsal scale rows usually 25 ; postocular dark stripe distinct and in contrast with the ground color ; a middorsal red- dish-brown or brown stripe evident anteriorly. Crotalus horridus atricaudatus Latreille (Coastal plain of South Atlantic and Gulf States; lower Mississippi Valley.) 20. Dorsal pattern consists of two parallel rows of small brown blotches Crotalus triseriatus pricei Van Denburgh (Mountains of southeastern Arizona to Durango, Mexico.) Dorsal pattern consists of a single row of large blotches. ... 21 21. Usually a single loreal ; tail rings sharply contrasting in color. Crotalus scutulatus scutulatus (Kennicott) (Southeastern California to west Texas, and south to the central Mexican plateau.) Usually two or more loreals ; tail often black, or with rings faintly in evidence against a dark background. Crotalus molossus molossus Baird and Girard (West Texas to central Arizona and south to northern Durango, Mexico.) Genus Diadophis * 1. Ventral color extending, on anterior portion of body, onto one or more of lowermost rows of dorsal scales ; ventrals usually more than 180 5 Ventral color not extending onto lowermost row ; ventrals usually less than 180 2 2. Black spots on belly in a single median row, or nearly or quite absent (very rarely irregular) ; upper labials usually 8 4 Black spots on belly numerous and scattered or irregular ; upper labials 7 (only rarely 8) * * Snakes of this genus are commonly called Ring-neck snakes. 30 Bulletin 16: Zoological Society of San Diego 3. Ventrals in males more than 145, in females more than 150; scale formula 17-17, or 17-15 (occasionally only 15) ; belly spots scattered or in pairs, generally clean-cut in appearance Diadophis punctatus arnyi Ivennicott (Ohio, northern Illinois, Indiana, Kansas, Iowa, South Dakota, Missouri, northwestern Arkansas, Oklahoma, and Texas.) Ventrals in males less than 145, in females less than 150; scale rows 15 ; belly spots showing tendency to fuse into a single row, or irregularly massed. Diadophis punctatus stictogenys Cope (Southern Illinois, through the lower Mississippi Valley to the Gulf.) 4. Sum of ventrals and caudals usually less than 191 ; belly with a series of large half -circular black spots along the median line ; neck ring usually partially or wholly inter- rupted on the mid-dorsal line. Diadophis punctatus punctatus (Linne) (Southeastern states northward to northern North Caro- lina.) Sum of ventrals and caudals usually more than 191 ; belly usually immaculate, but sometimes with a median series of small black spots, more or less imperfectly developed ; neck ring only rarely interrupted on the mid-dorsal line. Diadophis punctatus cdwardsii (Merrem) (The mountains of the Carolinas through the Appa- lachians northward to the Northern Peninsula of Michi- gan, Wisconsin, southern Canada, and the Maritime provinces.) 5. Ventrals in males less than 206 ; in females less than 220. ... 7 Ventrals in males more than 206 ; in females more than 220. . 6 6. Neck ring 2 to 4 scale lengths in width. Diadophis regalis arizonae Blanchard (Central Arizona to northern Sonora, Mexico.) Neck ring absent, or much reduced. Diadophis regalis regalis Baird and Girard (Southern Utah, southeastern Arizona, to central Texas and to the State of Veracruz, Mexico.) 7. Scale formula, 17-15 (rarely 15-15) 8 Scale formula, 15-15 or 15-13 (rarely 17-15 or 15-17-15) ... 9 8. Ventral color not covering more than % Qf the lowermost row of dorsal scales ; belly usually conspicuously spotted with black. .Diadophis amabilis niodestus Dumeril and Bocourt (San Bernardino Mountains, and Los Angeles County, in- cluding Santa Catalina Island, south to extreme northern San Diego County, California.) Perkins : A Key to the Snakes of the United States 31 Ventral color covering from iy2 to 2 of the lowermost rows of dorsal scales ; belly usually only lightly spotted with black Diadophis amabilis vandenburghi Blanchard (Ventura to Santa Cruz County, California.) 9. Ventral color usually covering more than % of the lower- most row of dorsal scales 10 Ventral color covering I/3 to % of the lowermost row of dorsal scales ; neck ring only rarely interrupted ; color above usually olive or bluish slate. Diadophis amabilis similis Blanchard (From southwestern San Bernardino County south into the San Pedro Martir range in Lower California.) 10. Neck ring from 1 to 1 l/2 scale lengths in width, often inter- rupted ; ventral color covering y2 to 1 /z rows of dorsal scales ; belly well sprinkled with small black spots ; dorsal color usually dark. Diadophis amabilis amabilis Baird and Girard (California, restricted to the regions about San Francisco and the San Joaquin and Sacramento Valleys.) Neck ring 1 /2 to 3 scale lengths in width, not interrupted; ventral color covering from l/2 to 2 or more rows of dorsal scales ; belly never heavily spotted with black 11 11. Two lowermost rows of dorsal scales flecked with black; belly rather conspicuously, although sparsely, marked with small black dots. . . .Diadophis amabilis occidentalis Blanchard (From Sonoma County, California, northward perhaps to the Columbia River.) Two lowermost rows of dorsal scales not flecked with black; belly almost or quite unspotted. Diadophis amabilis pulchollus Baird and Girard (Western slope of the Sierra Nevada, south perhaps to Tejon Pass in California and north perhaps to southern Oregon.) Genus Drymarchon 1 . General color black ; upper labial behind eye not in contact with lower anterior temporal. Indigo snake, Gopher snake Drymarchon corals couperi (Holbrook) (South Carolina to Florida, westward through southern Louisiana into Texas.) General color brown but posterior part of body and tail black ; upper labial behind eye usually in contact with lower anterior temporal. Drymarchon corals melanurus (Dumeril and Bibron) (Extreme southwestern Texas to northwestern South America.) 32 Bulletin 16: Zoological Society of San Diego Genus Drymobius Drymobius mar garitif erus (Schlegel) (Southwestern Texas to Venezuela and Colombia.) Genus Elaphe* 1. Suboculars present Elaphe subocularis (Brown) (Extreme southwestern Texas southward to near Saltillo, Mexico.) No suboculars (upper labials in contact with eye) 2 2. Upper surface uniform grayish or greenish ; uniform whitish below Elaphe chlorosoma (Gunther) (Santa Rita Mountains in Arizona, southward to Guerrero and Jalisco, Mexico.) Upper surface dark brown or black, or with blotches or stripes 3 3. Dorsal pattern consists of 50 or more (usually more) narrow dark cross-bands separated by wide interspaces. Elaphe bairdi (Yarrow) (Davis Mountains in Jeff Davis and Brewster Counties, Texas; also Coahuila, Mexico.) Dorsal pattern not of 50 or more narrow dark cross-bands . . 4 4. Neck bands traversing parietals and uniting on frontal 5 No neck bands traversing parietals and uniting on frontal. . 7 5. More than 222 ventrals ; red in the dorsal coloring 6 Less than 222 ventrals ; dorsal color gray and brown. Elaphe laeta (Baird and Girard) (Utah, Kansas, and Nebraska, southward to central Mex- ico.) 6. A great deal of black on the yellowish belly. Corn snake. Elaphe guttata (Linne) (New Jersey to Florida, to Louisiana and Arkansas.) No black (or very little) on pinkish belly, Elaphe rosacea (Cope) (The lower Florida Keys.) 7. More than 220 ventrals 8 Less than 220 ventrals. Fox snake. Elaphe vulpina (Baird and Girard) (Ohio westward to South Dakota, northward to Minne- sota, Wisconsin, and Michigan.) 8. Dorsal pattern in adults consists of four longitudinal stripes (the juveniles are blotched) ; caudals in males less than 88, in females 63 to 77 9 * Snakes of this genus are commonly called Rat snakes and Chicken snakes. Perkins: A Key to the Snakes of the United States 33 Dorsal pattern of blotches or uniform black ; caudals in males more than 88, females 69 to 95 10 9. No (or very indistinct) blotches between the middle stripes. Elaphe quadrivittata quadrivittata (Holbrook) (Eastern North Carolina to Florida and west to the Mississippi River.) Distinct blotches between the middle stripes. Elaphe quadrivittata deckerti Brady (The upper Florida Keys.) 10. Color above uniform black or nearly so (the juveniles are blotched) ; scale rows 25 or 27. Pilot black snake. Elaphe obsoleta obsoleta (Say) (Southern New England westward to Wisconsin, south- ern Ontario, southward to Texas, Louisiana and Florida.) Pattern of readily distinguishable blotches; scale rows 27 or 29 Elaphe obsoleta con finis (Baird and Girard) (South Atlantic and Gulf States and states of southern Mississippi Valley.) Genus Farancia * 1. Light bars on the neck separated medially by (usually) 8 or 9 scale rows ; light bars on body end abruptly dorsally. Farancia abacura reinwardtii Schlegel (Extreme western Florida northward in the lowlands to southern Indiana and southeastern Missouri ; westward along the coast of Texas.) Light neck bars separated by no more than 3 or 4 scale rows ; light bars on body becoming narrower dorsally and end in a point Farancia abacura abacura (Holbrook) (Peninsular Florida northward in the coastal regions to Amelia County, Virginia, westward to include extreme eastern Alabama.) Genus Ficimia 1. Small internasals separated by the rostral, which touches the prefrontals ; flecks of brown on posterior part of belly and under tail Ficimia cana (Cope) (Western Texas to Arizona.) No internasals; rostral separates the prefrontals and makes a broad contact with the frontal; belly uniform white. Ficimia streckeri Taylor (Extreme southeastern Texas.) * Snakes' of this genus are commonly called Horn snakes. 34 Bulletin 16: Zoological Society of San Diego Genus Haldca 1. 6 upper labials; 2 postoculars (seldom 1 or 3) 2 5 upper labials; 1 postocular Haldca striatula (Linne) (Virginia to northern Florida, westward to central Texas, Oklahoma and Missouri.) 2. 15 scale rows Haldca valeriac valeriac (Baird and Girard) (New Jersey to northern Florida, west to Ohio and Ten- nessee.) 17 scale rows Haldca valeriac elegans (Kennicott) (Indiana, Illinois and Iowa southward to Texas, eastward to southwestern Alabama, and northward to Ohio and western Pennsylvania.) Genus Hcterodon* 1. Prefrontals in contact; under side of tail generally conspicu- ously lighter than abdomen 2 Prefrontals separated by small scales; underside of tail not conspicuously lighter than abdomen 3 2. Internasals separated by a small scale, the azygous ; 20 or more light cross-bars on body ; some specimens nearly black above Hcterodon contortrix contortrix (Linne) (New Hampshire to central Florida, westward to Texas and Oklahoma and northward through the states of the Mississippi basin to Minnesota.) Internasals in contact; less than 20 light cross-bars on body. Hcterodon contortrix browni Stejneger (Extreme southern Florida.) 3. 23 scale rows; under surface mostly black 4 25 scale rows (rarely 27) ; under surface mostly light. Hcterodon shuns (Linne) (North Carolina southward to central Florida, and north- westward to Indiana.) 4. 2 or 3 small scales accessory to the azygous ; loreal small or absent ; under surface black and white spotted. Hcterodon nasicus kenncrlyi Kennicott (Western Texas, southern New Mexico, southern Arizona and northwestern Mexico.) 8 or more small scales accessory to the azygous ; loreals gen- erally 2 ; undersurface nearly all black. Hcterodon nasicus nasicus Baird and Girard (Southwestern Iowa, Kansas, Nebraska, and Colorado, north to Montana and south to northern Mexico ; also southeastern Missouri.) * Snakes of this genus are commonly called Hog-nose snakes and Spread- ing adders. Perkins: A Key to the Snakes of the United States 35 Genus Hypsiglena Hypsiglena ochrorhynchus Cope. (Central Washington and Idaho southeastward through southern Utah and southern Colorado to Kansas then southwestward to southwestern Texas and west to Cali- fornia; northwestern Mexico, Lower California and Cedros Island.) Genus Lampropeltis* 1. Pattern of narrow cross-bands of black, the alternate bands mixed or split with red ; ground color above slate gray. Lampropeltis alterna (Brown) (Davis Mountains, Texas.) Pattern not of narrow cross-bands of black, the alternate bands mixed with red ; ground color above not slate gray . . 2 2. Pattern with red, or with dorsal blotches of brown, gray, or red, with black borders 12 Pattern not with red, nor with dorsal blotches of brown, gray, or red, with black borders 3 3. Pattern in rings, cross-bands, or stripes, or chiefly of scales white at base shading gradually into a black distal border, but not chiefly of sharply defined white or yellow spots on black scales 6 Scales chiefly black with sharply defined white or yellow spots, these spots often so grouped as to form 50 or more narrow cross-bands on body and tail 4 4. Usually 21 scale rows at the middle of the body 5 Mid-body scale rows 23 or 25 ; no light centers dorsally on the scales between the cross-bands ; head mostly black. Lampropeltis getulus splendid a (Baird and Girard) (Southeastern Arizona; southern Texas and northern Mexico.) 5. A yellow spot on practically every dorsal scale. Lampropeltis getulus holbrooki Stejneger (Western Alabama to Texas, northward through the states of the Mississippi basin mostly west of the river, to south- ern Iowa, southern Nebraska, and Wyoming.) Scales between the cross-bands without light centers or with only a very few small ones. J * % # Lampropeltis getulus nigra (Yarrow) (Northern Alabama, Tennessee, West Virginia, Kentucky, Ohio, and southern Indiana.) * Snakes of this genus are commonly called King snakes and Milk snakes. 36 Bulletin 16 : Zoological Society of San Diego 6. Pattern consists of rings, or longitudinal stripes of white or yellowish ; posterior chin-shields generally much shorter and narrower than anterior and separated by 1 or 2 small scales 9 No rings nor stripes ; posterior chin-shields nearly as long and nearly as wide as anterior, in contact or separated by not more than 1 small scale 7 7. Many dorsal cross-bands of white or yellow 8 No dorsal cross-bands distinguishable; dorsal scales light at base, shading gradually into a dark distal border. Lampropeltis get ulus brooksi Barbour (Extreme southern Florida.) 8. Less than 50 cross-bands. . Lampropeltis getulus getulus (Linne) (Southern New Jersey to northern Florida and south- eastern Alabama.) More than 50 cross-bands, or nearly indistinguishable. Lampropeltis getulus floridana Blanchard (Florida from Orange County in the north to central Dade County in the southeast.) 9. Pattern of rings 10 A dorsal longitudinal stripe. Lampropeltis getulus calif orniae (Blainville) (Southwestern California and Lower California.) 10. White scales white to their bases; white bars on prefrontals broad 11 White scales mostly brown at their bases ; white bars on prefrontals narrow. Lampropeltis getulus yumensis Blanchard (Southwestern Arizona, California, as far north as Blythe, and as far west as Seeley, and adjacent areas of Sonora, Mexico and Lower California.) 11. If found within the territory where striped or aberrant pat- tern phases are found. Lampropeltis getulus calif orniae (Blainville)* (Southern San Joaquin Valley, through southern Cali- fornia, and Lower California.) If found outside the territory where striped or aberrant pattern phases are found. Lampropeltis getulus boylii (Baird and Girard)* (California, except San Joaquin Valley and southern Cali- fornia; southern Oregon, Nevada, Utah, and western Arizona.) * See L. M. Klauber : The California King Snake, a case of pattern dimorphism. Herpetologica, Vol. 1, No. 1, July 11, 1936. Also Klauber: Pattern dimorphism in the California King Snake, Bull., Zool. Soc. San Diego, No. 15, 1939. Perkins : A Key to the Snakes of the United States 37 12. Pattern of black-edged dorsal blotches of brownish or dark red, only narrowly in contact with fifth row of scales, or extending no lower than the sixth or seventh rows 13 Pattern in rings ; or if in blotches or saddles of brown, gray, or red, these broadly in contact with the fifth or a lower row of scales 14 13. Scale rows 25 or 27 ; dorsal blotches have concave anterior and posterior margins; lower labials 9 or 10, rarely 8. Lampropeltis calligaster (Harlan) (Indiana, Illinois, Wisconsin, and southern Iowa; Mis- sissippi, Kansas, Arkansas, Oklahoma and Texas.) Scale rows 23 or 21 ; dorsal blotches with straight or convex anterior and posterior margins; blotches often indistinct; lower labials 8, less often 9. Lampropeltis rhombomaculata (Holbrook) (Maryland to central Florida and part of Alabama.) 14. Whitish cross-bands on body and tail less than 40; or if more than 40, snout not uniformly whitish 15 Whitish cross-bands more than 40 ; top of head black, snout uniformly white Lampropeltis pyromelana (Cope) (Utah, Arizona, and western New Mexico.) 15. Whitish cross-bands usually distinctly widened on first row of scales, or scale rows anteriorly not more than 17 19 Whitish cross-bands little, if any, widened on the lower rows of scales, and scale rows more than 17 on anterior end of of body 16 16. Whitish rings usually more than 30; snout black. Lampropeltis multicincta (Yarrow) (Oregon, California and Lower California.) Whitish rings less than 30 17 17. Dorsal red areas usually continuous across the belly; snout whitish, speckled with black. Lampropeltis triangulum amaura Cope (Lower Mississippi Valley, southeastern Oklahoma, and eastern Texas.) Spaces on the belly between the yellow rings filled with black ; snout totally black or only very slightly lightened on top or sides 18 18. Yellowish rings, 19 to 25 ; black spaces on the belly usually longer than the intervening yellow ones. Lampropeltis triangulum annulata Kennicott (Southeastern Texas and northeastern Mexico.) 38 Bulletin 16: Zoological Society of San Diego Yellowish rings usually 25 to 30; black spaces on belly usually shorter than the intervening yellow ones. Lampropeltis triangulum gentilis (Baird and Girard) (Texas and northwestern Mexico; Arizona, Utah, Colo- rado. to South Dakota.) 19. Black on the head practically restricted to the posterior por- tion, or to various black-edged light markings 21 Black practically uniform over head except for snout region, which is more or less lightened, at least on the sides 20 20. Whitish rings or cross-bands usually 25 to 30. Lampropeltis triangulum gentilis (Baird and Girard) (Texas and northwestern Mexico; Arizona, Utah, Colo- rado to South Dakota.) Whitish rings or cross-bands 18 to 25. Lampropeltis triangulum amaura Cope (Lower Mississippi Valley, southeastern Oklahoma, and eastern Texas.) 21. Usually two anterior temporals; scale formula very rarely lower than 19-21-19-17 23 Usually one anterior temporal ; scale formula generally 17-19-17 ; rarely higher than 19-17 22 22. Red areas continuous across the belly. Lampropeltis elapsoides elapsoides (Holbrook) (Kentucky, Tennessee, and North Carolina, southward throughout the southeastern coastal plain, including all of Florida.) Red not continuous across the belly but restricted to black- bordered dorsal saddles that extend upon the ventrals. Lampropeltis elapsoides virginiana Blanchard (Northern North Carolina to Delaware, east of the Alle- ghany Mountains.) 23. Dorsal pattern of saddles, or of blotches of red or brown ; whitish cross-bands 23 to 60 24 Dorsal pattern practically rings ; whitish cross-bands 18 to 30. Lampropeltis triangulum amaura Cope (Lower Mississippi Valley, southeastern Oklahoma, and eastern Texas.) 24. Dorsal saddles usually more than 35, reaching down to the fifth or third row of scales above the ventrals; often two rows of lateral alternating blotches ; a dark band on pos- terior portion of prefrontals; a black-bordered light band from the eye to the angle of the mouth; usually a Y- shaped light spot on the back of the head. Lampropeltis triangulum triangulum (Lacepede) Perkins: A Ivey to trie Snakes of the United States 39 (Eastern North America from Maine through Ontario to Minnesota, south to Iowa and Virginia and in the mountains farther south.) Dorsal saddles usually less than 35, extending down to the third row of scales, or lower ; only one series of alternating spots ; head markings of triangulum only partially or not at all developed Lampropcltis triangulum syspila (Cope) (Oklahoma, Arkansas, and Tennessee northward to Kansas, Iowa, Illinois, Indiana, and southern Minnesota.) Genus Leptodeira Leptodeira septentrionalis septcntrionalis (Ivennicott) (Southern Texas and northeastern Mexico.) Genus Leptotyphlops* 1. Supraoculars present 2 No supraoculars 3 2. Anterior supralabials entire. Leptotyphlops dulcis dulcis (Baird and Girard) (Central Oklahoma south through central Texas to north- ern Nuevo Leon and Tamaulipas, Mexico.) Each anterior supralabial divided by a vertical suture. Leptotyphlops dulcis dissectus (Cope) (Coahuila, Mexico, trans-Pecos Texas, southern New Mexico and southeastern Arizona ; also southern Kansas and northeastern Oklahoma.) 3. 10 scale rows around the tail. Leptotyphlops humilis segregus Klauber (Southeastern Arizona through trans-Pecos and Big- Bend, Texas to central Coahuila, Mexico.) 12 scale rows around the tail 4 4. 4th mid-dorsal scale often divided longitudinally; 5th dorsal much wider than the 6th ; dorsal scales more than 288. Leptotyphlops humilis utahensis Tanner (Extreme southwestern Utah.) 4th mid-dorsal scale undivided; 5th dorsal not much, if any, wider than the 6th; dorsal scales more or less then 288. . . 5 * Adapted from L. M. Klauber: The Worm Snakes of the Genus Lep- totyphlops in the United States and Northern Mexico. Trans. S. D. Soc. Nat. Hist. Vol. 9, No. 18. April, 1940. 40 Bulletin 16: Zoological Society of San Diego 5. 5 lightly pigmented mid-dorsal scale rows; usually 285 or more dorsal scales. . . .Leptotyphlops humilis cahuilae Klauber (The Colorado Desert in southeastern California, the Yuma Desert in southwestern Arizona, and Vizcaino Desert in central Lower California.) 7 or more heavily or mediumly pigmented mid-dorsal scale rows ; usually less than 285 dorsal scales. Leptotyphlops humilis humilis (Baird and Girard) (Central Lower California including Cedros Island north to Santa Barbara, California; the Mojave Desert; from extreme southern Nevada southeasterly to the Tucson area in Arizona.) Genus Lichanura 1. Stripes (usually poorly defined) have uneven (wavy or mottled) edges. California Boa. Lichanura roseofusca roseofusca Cope (Southwestern California and northern Lower Cali- fornia.) Stripes (well defined) have even (but serrated) edges Desert Boa Lichanura roseofusca gracia Klauber (Desert regions of southeastern California, northeastern Lower California, southwestern Arizona and western Sonora.) Genus Liodytes Liodytes alleni (Garman) (Florida and the Okefinokee Swamp, Georgia.) Genus Micruroides Micruroides euryxanthus (Ivennicott) Coral snake. (Southern New Mexico and Arizona, possibly extreme southwestern Utah, northern Mexico and Tiburon Is- land.) Genus Micrurus * 1. No black on the dorsal scales of the red rings. Micrurus f ulvius harhouri Schmidt (Extreme southern Florida.) Black marking on the dorsal scales of the red rings 2 * Snakes of this genus are commonly called Coral snakes. Perkins: A Key to the Snakes of the United States 41 2. Many irregular black streaks and spots in the red rings. Micrurus fulvius tenere (Baird and Girard) (Mississippi, west through Texas to northern Tamaulipas, Mexico.) Black markings in red rings tend to form two large spots. Micrurus fulvius fulvius (Linne) (North Carolina to Florida; the Gulf States and Mis- sissippi Valley States north to Ohio and Indiana.) Genus Natrix * 1. Scale rows 19 2 Scale rows more than 19 5 2. Lower labials 7 ; one preocular. . . .Natrix kirtlandii (Kennicott) (V isconsin and southern Michigan south through north- ern and central Illinois and Indiana to Louisville, Ken- tucky, and east throughout Ohio to western Pennsyl- vania.) Lower labials 9 to 11; usually 2 preoculars 3 3. One long dark median stripe on belly, or no markings except on the ends of ventrals. . .Natrix grahamii (Baird and Girard) (Illinois to eastern Kansas and south to Texas and Louisiana.) Two long dark stripes near middle of belly, at least anteri- orly 4 4. Light ventro-lateral stripes present. .Natrix septemvittata (Say) (Pennsylvania, Ohio, Michigan, and Wisconsin south to Alabama, Georgia and northeastern Florida.) No light ventro-lateral stripes Natrix rigid a (Say) (South Carolina to western Louisiana, excluding penin- sular Florida.) 5. Scale rows 27 to 33 (sometimes 25 in rhombifera , which has, however, a pattern of alternating dorsal and lateral spots connected by diagonal bars) ; lower labials usually 11 to 13 6 Scale rows 21 to 25 (rarely 27 in transversa ) ; lower labials usually 10 9 6. Two anterior temporals ; a mid-dorsal row of 21 to 25 isolated quadrate spots Natrix taxis pilota (Holbrook) (Coastal regions from North Carolina to central Florida and westward possibly to Louisiana.) One anterior temporal ; dorsal spots, if visible, usually con- nected with lateral spots 7 * Adapted from William M. Clay: A Synopsis of the North American Water Snakes; Copeia, 1938, No. 4. 42 Bulletin 16: Zoological Society of San Diego 7. No suboculars (upper labials in contact with eye) ; dorsal spots, 26 to 33. . . .Natrix rhombifera rhombifera (Hallowed) (Southern Indiana and Illinois to Alabama and west to Texas and northern Mexico.) One or more suboculars ; dorsal spots about 50, small and ill-defined 8 8. Ventral surface of posterior two-thirds of body heavily marked with dark brown; 41 to 50 lateral bars; caudals in males less than 80, in females less than 70. Natrix cyclopion cyclopion (Dumeril and Bibron) (Lowlands of the Mississippi Valley from southern Ill- inois south to Louisiana, east to northwestern Florida and possibly west along the coast into Texas.) Ventral surface whitish or yellowish, only slightly marked posteriorly ; 49 to 57 lateral bars ; caudals in males 80 or more, in females 70 or more. . .Natrix cyclopion floridana Goff (Peninsular Florida, northwest to Tallahassee and north- east along the coast to South Carolina.) 9. A median (sometimes irregular) row of light spots on belly. 10 No median row of light spots on belly 11 10. Dorsal surface spotted or unicolor, the spots occasionally tending to form longitudinal stripes, especially anteriorly. Natrix sipedon compressicauda (Kennicott) (Coast of the southern half of peninsular Florida and ad- jacent coast of Cuba, mainly in brackish water.) Dorsal surface with four longitudinal dark stripes. Natrix sipedon clarkii (Baird and Girard) (Gulf coast from Levy County, Florida, to San Patricio County, Texas, occurring primarily in brackish water.) 11. Dorsal surface unicolor 12 Dorsal surface with cross-bands or spots 13 12. Dorsal surface gray ; belly yellow to cream, dusky posteriorly, especially tail Natrix sipedon insularum Conant and Clay (Pelee and other islands in the western portion of Lake Erie.) Dorsal surface uniformly dark brown, reddish brown, or black (or spots faintly visible) in adults; bellv yellow or red, immaculate or with dark antero-lateral margins of ventrals, but without definite spots, and tip of tail with- out markings. . . .Natrix erythrogaster erythrogaster (Forster) (Eastern Texas, eastern Oklahoma and southeastern Kan- sas eastward throughout the southern states (excluding peninsular Florida) and north to Pennsylvania, Ohio, and extreme southern portions of Michigan and Wisconsin.) Perkins: A Key to the Snakes of the United States 43 13. \ entral surface immaculate or with dark antero-lateral margins of ventrals ; tail immaculate beneath, including tip Ventral surface with definite markings ; tip of tail never im- maculate beneath 14 15 14. Neck region with 1 to / cross-bands, followed posteriorly by a median series of spots in alternation with a lateral series ; this pattern becomes obsolete and uniformly dark with maturity. Juvenile Natrix erythrogaster erythrogaster ( Forster ) (Eastern Texas, eastern Oklahoma and southeastern Kan- sas eastward throughout the southern states (excluding peninsular Florida) and north to Pennsylvania, Ohio, and extreme southern portions of Michigan and Wisconsin.) Pattern similar but with 2, 1, or no anterior transverse bands, and not becoming obsolete. Natrix erythrogaster transversa (Hallowed) (Western Missouri and eastern Kansas through western Oklahoma to southeastern New Mexico, east to Ft. Worth and Houston, Texas, and south to Nuevo Feon, Mexico.) 15. Dorsal pattern of 3 to 15 anterior transverse bands, posterior to which a series of median dorsal blotches alternates with a series of lateral spots (rarely a complete series of trans- verse bands, but then belly has half -moon shaped spots) ; ventrals 128 to 155 16 Dorsal pattern wholly of transverse bands or rarely with a few alternating spots; ventrals 121 to 143 17 16. Usually 3 to 10 (rarely more) anterior transverse bands and a total of more than 30 bands and dorsal spots on body ; lateral interspaces narrower than lateral bars. Natrix sipedon sipedon (Finne) (Southern Maine through southern Quebec, southern On- tario, and Wisconsin to eastern Colorado, south to Okla- homa, Tennessee, and northwestern South Carolina.) Usually 5 to 15 anterior transverse bands and a total of less than 30 bands and dorsal spots ; lateral interspaces wider than lateral bars Natrix sipedon pleuralis Cope (South Carolina westward around the southern extremity of the Appalachian Mountains, Mississippi, Arkansas, and southern Missouri, and northward to southern Illinois and southern Indiana.) 17. Dorsal bands 18 or less Natrix sipedon confluens Blanchard (From the Mississippi River west along the Gulf to central Texas and north to southern Oklahoma, central Arkansas, southeastern Missouri and extreme southern Illinois.) Dorsal bands more than 18 18 44 Bulletin 16: Zoological Society of San Diego 18. Dorsal bands about 24 ( 19 to 33) ; ventrals usually more than 128; belly with quadrate dark or red spots; sometimes small lateral spots alternate with the transverse bands. Natrix sipcdon fasciata (Linne) (Coastal region from North Carolina to southeastern Louisiana, excluding peninsular Florida.) Dorsal bands about 29 (24 to 35) ; ventrals usually less than 128; belly with reddish or dark anterior borders to ven- trals, these often narrowed in center leaving a light area. Natrix sipcdon pictiventris Cope (Peninsular Florida.) Genus Opheodrys 1. Scales keeled. Rough green snake. .Opheodrys aestivus (Linne) (Connecticut to Florida, westward to eastern New Mex- ico ; in the Mississippi drainage basin found in the south- ern portion and northward to Kansas, Illinois and Ohio.) Scales smooth. Smooth green snake. Opheodrys vernal is (Harlan) (Utah, New Mexico, and Texas, northeastward to North Dakota and Illinois, thence eastward through New Jersey and through New England to southern Canada.) Genus Oxybelis Oxyhelis micro phthalmns Barbour and Amaral. (Desert mountain canyons of Arizona near the inter- national Boundary.) Genus Phyllorhynchus * 1. Dorsal body blotches (not including tail spots) less than 17. . 2 Dorsal body blotches (not including tail spots) 17 or more. . 3 2. Ventrals in males, 166 or less; in females, 179 or less. Caudals in males, 36 or less; in females, 26 or less. Body blotches considerably wider, along the dorsal line, than the interspaces Phyllorhynchus brozvni browni Stejneger (Southeastern Pinal County and eastern Pima County, west to Organ Pipe Cactus National Monument, Pima County, Arizona.) Ventrals in males, 167 or more; in females, 180 or more. Caudals in males, 37 or more ; in females, 27 or more. Body blotches little, if any, wider, along the dorsal line, than the interspaces . .Phyllorhynchus brozvni Incidns Klauber (Northeastern Maricopa County, Arizona.) * Adapted from L. M. Klauber: Two New Subspecies of Phyllorhynchus, the Leaf-nose snake, with notes on the genus. Trans. S. D. Soc. Nat. Hist. Vol. 9, No. 20, April, 1940. Perkins: A Key to the Snakes of the United States 45 3. Ventrals in males, 168 or more; in females, 179 or more. Body blotches usually distinctly narrower, along the dorsal line, than the interspaces. Phyllorhynchus decurtatus perkinsi Klauber (Deserts of southern California, extreme southern Ne- vada, western Arizona, northeastern Lower California, and extreme northwestern Sonora, Mexico.) Ventrals in males, 167 or less; in females, 178 or less. Body blotches usually equal to or wider, along the dorsal line, than the interspaces. Phyllorhynchus decurtatus nubilus Klauber (Vicinity of Tucson, Arizona; west central and north- western Sonora, Mexico.) Genus Pit uo phis * 1. 2 prefrontals. . . . Pituophis deppei deppei (Dumeril and Bibron) (Hays County, Texas, to southern Oaxaca, Mexico.) More than 2 prefrontals 2 2. Rostral penetrating between internasals, conspicuously higher than wide 3 Rostral not, or but slightly, penetrating between internasals, about as high as wide 8 3. Dorsal blotches prominent 4 Dorsal blotches weak or missing 7 4. Dorsal blotches less than 35 . .Pituophis melanoleucus (Daudin) (Pine barrens of southern New Jersey to South Carolina, west to Tennessee.) Dorsal blotches 35 or more 5 5. 6. Dorsal coloring white (not yellow) suffused with brown. Pituophis ruthveni Stull (Louisiana.) Dorsal coloring yellow (not white), not suffused with brown 6 Apex of rostral narrow and sharp; dorsal blotches 40 to 65. Pituophis sayi sayi (Schlegel) (Northern Mexico and Texas north to Indiana, Wisconsin, and Alberta.) Apex of rostral blunt; dorsal blotches 35 to 55. Pituophis sayi affinis Hallowed (Northern Mexico north through New Mexico and Ari- zona to southern Colorado.) * Snakes of this genus1 are commonly called Pine snakes, Bull snakes, and Gopher snakes. 46 Bulletin 16: Zoological Society of San Diego 7. Dorsal pattern a suffusion of rusty brown. Pituophis mugitus Barbour (Peninsular Florida.) Uniform black above and below. . . .Pituophis lodingi Blanchard (Southern Alabama.) 8. Dorsal dark blotches much wider than lighter interspaces ; anterior dorsal blotches slightly, if at all, joined to lateral spots 9 Dorsal dark blotches little, if any, wider than lighter inter- spaces; dorsal blotches often fused with lateral spots giving a checkerboard or a banded appearance. Pituophis catenifer annectens Baird and Girard (Coast region of southern California and northern Lower California.) 9. Ventrals usually less than 225. Pituophis catenifer catenifer (Blainville) (Los Angeles county north through western California to British Columbia.) Ventrals usually more than 225. Pituophis catenifer deserticola Stejneger (Southeastern California, Nevada, Utah, western Colo- rado, Idaho, and eastern parts of Oregon and Washing- ton; northeastern Lower California.) Genus Rhadinaea Rhadinaea flavilata (Cope) (Eastern North Carolina to Florida, and along the Gulf coast to central Texas.) Genus RhinocheUus Rhinocheilus lecontei Baird and Girard (Western Kansas south through western Texas to north- ern Mexico ; westward, as far north as southern Idaho, to the Pacific and south through California and Lower California.) Genus Salvador a * 1. Posterior pair of chin-shields in contact or separated by 1 small scale ; loreal single. Salvadora grahamiae grahamiae Baird and Girard (Southeastern Arizona eastward through New Mexico and Texas, except the extreme eastern part.) * Adapted from Charles M. Bogert : The Patch-nosed Snakes; Pub. Univ. Calif., L. A. Biol. Sci. Vol. 1, No. 10, 1939. Perkins : A Key to the Snakes of the United States 47 Posterior pair of chin-shields separated by 2 or 3 small scales; loreals 2 or 3 2 2. Top of the head gray, about the color of the light stripe; each of the dark stripes splitting into two stripes on the posterior % of the body .Salvador a grahamiae hex ale pis (Cope) (Southern and western Arizona, southwestern Utah, southern and western Nevada to southeastern California, Lower California and Tiburon Island; and western Mexico.) Top of head brown, about the color of the dark stripes ; each dark stripe splitting into two stripes on the posterior Yz of the body Salvadora grahamiae virgultea Bogert (Foothills of southwestern California and northwestern Lower California.) Genus Seminatrix Seminatrix pygaea (Cope) (Cartaret County, North Carolina, southward through the Florida peninsula.) Genus Sistrurus* * L Upper preocular usually in contact with postnasal; usually 3 upper labials in contact with the pit-border scales ; 1 1 or more dorsal scale rows at center of tail ; no red or orange in the inter-blotch spaces on the mid-dorsal line 2 Upper preocular not in contact with postnasal ; usually 2 upper labials in contact with pit-border scales ; 10 or less dorsal scale rows at center of tail ; usually with red or orange between the blotches on the mid-dorsal line 3 2. Ventral surface dark, heavily clouded with black blotches, often almost solid black ; scale rows usually 25 ; body blotches usually less than 37. A pattern of square, red- brown, or black blotches on a gray-brown ground ; some- times unicolor black. Massasauga. Sistrurus catenatus catenatus (Rafinesque) (Central New York west to eastern Oklahoma.) Ventral surface mottled or spotted, the dark areas being less extensive than the light ; scale rows often 23 ; body blotches usually more than 36. A pattern of dark red-brown blotches on a gray-brown ground. Sistrurus catenatus tergeminus (Say) (Southwestern plains from central Kansas to northern Tamaulipas, Mexico and southeastern Arizona.) * Adapted from L. M. Klauber; A Key to the Rattlesnakes with Summary of Characteristics'; Trans. S. D. Soc. Nat. Hist., Vol. 8, No. 20, 1936. * Snakes of this genus are commonly called Ground rattlers. 48 Bulletin 16: Zoological Society of San Diego 3. Dorsal coloration brown or light-gray ; ventral surface cream, moderately flecked with brown or gray; head markings distinct; lateral spots in 1 or 2 series 4 Dorsal coloration dark-gray to black; ventral surface white, heavily blotched with dark-brown or black ; head mark- ings obscure ; lateral spots in 3 series. Sistrurus miliarius barbouri Gloyd (The Gulf lowlands from Georgia to Mississippi ; Florida.) 4. Dorsal scale rows usually 21 ; dorsal spots wider than long and with irregular edges ; lateral spots usually higher than wide ; ventral spots confined to individual plates. Sistrurus miliarius streckeri Gloyd (Southern Missouri to Louisiana and west to central Texas.) Dorsal scale rows usually 23 ; dorsal spots oval or subcircular, edges even ; lateral spots usually round ; ventral spots usually occupying two adjacent plates. Sistrurus miliarius miliarius (Linne) (North Carolina to central Alabama.) Genus Sonora * 1. Snout normal; abdomen rounded or but slightly angulate ; scale rows various 2 Snout distinctly flattened and attenuated ; abdomen strongly angulate; scale rows 15-15 ... .Sonora occipitalis (Hallowell) (Southeastern California, southern Nevada, and in south- ern Arizona as far east as Tucson.) 2. Anterior scale rows 15, rarely 14 or 16; ventral count high. . 3 Anterior scale rows 13, rarely 14; ventral count low, in males 126 to 139, in females 136 to 148. Sonora taylori (Boulenger) (Southern Texas and northeastern Mexico.) 3. Scale rows, near anus 15, rarely 14; ventrals in males 134 to 155, in females 140 to 162; caudals in males 39 to 52, in females 31 to 44 Sonora episcopa (Ivennicott) (Central Texas north to southeastern Kansas and south- western Missouri and west to extreme eastern Colorado and New Mexico.) Scale rows near anus 14, very rarely 15 or 13; ventrals or caudals running distinctly higher 4 * Adapted from William H. Stickel : The Snakes of the Genus Sonora in the United States and Lower California; Copeia, 1938, No. 4. Perkins: A Key to the Snakes of the United States 49 4. Ventrals in males 153 to 168, in females 162 to 183; caudals in males 41 to 57, in females 37 to 54 5 Ventrals in males 147 to 155, in females 157 to 166; caudals in males 53 to 59, in females 46 to 51. Sonora semiannulata blanchardi Stickel (Southwestern Texas and New Mexico, and adjacent Mexico.) 5. A regular series of dark cross-bands present 6 No series of cross-bands 7 6. Most of the body bands meeting across the abdomen ; lateral scales heavily shaded with gray. Sonora semiannulata gloydi Stickel (Lower Sonoran level of the Grand Canyon, Arizona.) Bands not meeting across abdomen, or only a few so meet- ing ; lateral scales lightly shaded with gray, or not shaded. Sonora semiannulata semiannulata Baird and Girard (Arizona, Utah, Nevada; Inyo County, California; Snake River region, Idaho; Sonora, Mexico.) 7. A sharp-edged dorsal pink stripe present ; stripe contrasting with the bluish-gray to brownish-gray lateral scales. Sonora miniata linearis Stickel (Southeastern California, Pershing County, Nevada, and the Cocopah Mountains, Lower California.) Dorsal pink stripe absent or blending gradually with the grayish to reddish color of the sides. Sonora miniata miniata Stickel (South central x\rizona and Ada County, Idaho.) Genus Stilosoma Stilosoma extenuatum Brown (Central Florida.) Genus Storeria 1. 17 scale rows Storeria dekayi (Holbrook) (Eastern North America, Ontario to Vera Cruz, Mexico, west to Kansas.) 15 scale rows 2 2. Ventral surface reddish without spots; ventrals less than 135 S' toreria occipitomaculata ( Storer ) (From Ontario and Lake Superior southward to Vera Cruz, Mexico, westward to Kansas, Iowa, and North Dakota, and southeastward through Alabama and Georgia into northern Florida.) Ventral surface pale with a row of black dots along each side ; ventrals more than 135 Storeria victa Hay (Florida and southern Georgia.) 50 Bulletin 16: Zoological Society of San Diego Genus Tantilla * 1. A light band on back of head crossing tips of parietals 2 A light band on back of head crossing behind parietals, or absent 4 2. A dark band, bordering light band posteriorly, broad (two to four scale lengths in width) ; eye small, its diameter less than half its distance from snout; ventrals less than 149. . 3 A dark band, bordering light band, narrow (one-half to one and one-half scale lengths in width) eye large, its diameter more than half its distance from snout; ventrals 149 or more Tantilla wilcoxi Stejneger (Huachuca Mountains, Arizona.) 3. Ventrals in males more than 130; in females 139 to 148; light band on back of head well defined although often interrupted on the mid-line. Tantilla coronata coronata Baird and Girard (South Carolina to southeastern Louisiana, north into western Kentucky.) Ventrals in males less than 130; in females 123 to 145 ; light band on back of head usually more or less obliterated. Tantilla coronata wagneri (Jan) (Peninsular Florida.) 4. Upper labials usually seven (the sixth approximately as long as the fifth) ; postoculars usually two, rarely single; head black or dark brown above, contrasting with the gen- eral dorsal color 5 Upper labials usually six (when seven, the sixth usually much shorter than the fifth) ; rarely more than one postocular; head usually but little darker than the body color above. Tantilla gracilis Baird and Girard (Missouri and southeastern Kansas to eastern Texas.) 5. Black of head extending three to five scale lengths behind parietal suture, not bordered behind with a narrow white band ; mental plate usually separated from chin-shields by first lower labials 6 Black of head usually extending only one or two scale lengths behind parietal suture, usually bordered behind with a narrow white band ; mental plate usually in contact with chin-shields 8 6. Black of head very convex or even pointed behind in the median line, not extending laterally on the last two upper labials nor reaching nearly or quite to the mouth line below the eyes 7 * Adapted from Frank N. Blanchard: Field Mus. Chicago, Zool. Ser., Vol. 20, No. 28, 1938. Perkins : A Key to the Snakes of the United States 51 Black of head straight across posteriorly, extending laterally on one or both last two upper labials, and reaching nearly or quite to the mouth line below the eyes. T an till a c oronata wa gneri ( Jan ) (Peninsular Florida.) 7. Ventrals less than 145 Tantilla kirnia Blanchard (Comanche County, Oklahoma, southward through Texas nearly to Brownsville, westward to San Antonio.) Ventrals more than 145 Tantilla nigriceps Kennicott ( Western Kansas and eastern Colorado southward through Oklahoma to Texas, New Mexico and southern Arizona.) 8. Black of head extending below angle of mouth onto gular scales Tantilla eiseni Stejneger (Fresno County, California, to northern part of Lower California.) Black of head not extending below angle of mouth onto gular scales 9 9. Ventrals in males less than 150, in females less than 160. Tantilla atriceps (Gunther) (Oklahoma, western Texas, New Mexico, southeastern Arizona to northern Mexico.) Ventrals in males more than 150, in females more than 160. Tantilla utahensis Blanchard (Southwestern Utah and west into Sierra Nevada in California.) Genus Thamnophis* * 1. Lateral stripe anteriorly on 3rd and 4th rows of scales 2 Lateral stripe anteriorly not on 4th row of scales or absent. . . 7 2. Tail usually more than 0.27 of total length 3 Tail usually less than 0.27 of total length 5 3. Upper labials usually 7. .Thamnophis sauritus sauritus (Linne) (Michigan, Ontario, and Maine, south to Mississippi, Alabama and Georgia.) Upper labials usually 8 4 4. Dorsal stripe present throughout. Thamnophis sauritus proximus (Say) (Northern Iowa and southern Wisconsin, west to western Nebraska and southeastern Colorado and south through Texas and Louisiana to Costa Rica.) Dorsal stripe absent, or present only behind the head. Thamnophis sauritus sackcnii (Kennicott) (Throughout Florida to southern Mississippi.) *The ordinoides group and the Pacific Coast subspecies of sirtalis are adapted from a forthcoming publication by Henry S. Fitch. *Snakes of this genus are commonly called Garter snakes and Ribbon snakes. 52 Bulletin 16: Zoological Society of San Diego 5. Scale formula usually 21-19-17; upper labials 8 (occasion- ally 9) Thamnophis megalops (Kennicott) (Mexico north to Texas, southwestern New Mexico and Arizona, and the Cocopah Mountains, Lower California.) Scale formula usually lower than 21-19-17; upper labials usually less than 8 6 6. Scale formula usually 19-21-19-17 ; upper labials usually 7 Thamnophis radix (Baird and Girard) (The Great Plains from Missouri to the Canadian North- west.) Scale formula usually 19-17 ; upper labials 6 or 7. Thamnophis butleri (Cope) (Extreme western New York, and southwestern Ontario; western Pennsylvania, through Ohio and Indiana, south- ern Michigan and Wisconsin.) 7. Lateral stripe anteriorly on 2nd and 3rd rows of scales, or absent 8 Lateral stripe on 3rd row of scales only. Thamnophis marcianus (Baird and Girard) (Kansas, Oklahoma and Texas west to southeastern Cali- fornia and northwestern Mexico.) 8. 7 upper labials 9 8 upper labials 15 9. Ventrals usually more than 153; dorsal stripe bright yellow; no pale dorsolateral flecks ; posterior chin-shields markedly longer than anterior 10 Ventrals usually less than 153; dorsal stripe yellow or red; pale yellowish flecks between scales in area between dorsal and lateral stripes ; posterior chin-shield but little longer than anterior. Thamnophis ordinoides ordinoides (Baird and Girard) (Coast region of northern California to British Columbia.) 10. Both rows of lateral spots distinct on the skin ; interspaces not usually red Thamnophis sirtalis sirtalis (Linne) (Eastern United States and Canada west to Minnesota, Wisconsin, Missouri, southward to eastern Texas.) Upper row of lateral spots fused on the skin; interspaces usually red 11 11. Ground color jet black obscuring dorsal spots and extending onto ventral surface ; stripes narrow and sharply defined, or occasionally with lateral stripes entirely obscured in melanistic individuals 12 Ground color paler, slaty or brownish, with little or no black on ventral surface except at tips of ventrals 13 Perkins: A Key to the Snakes of the United States 53 12. Head red; dorsal stripe one and two half scales wide. Thamnophis sirtalis concinnus (Hallowed) (Northwestern Oregon.) Head dark colored with no reddish suffusion ; dorsal stripe nearly confined to mid-dorsal row. Thamnophis sirtalis pickcringii (Baird and Girard) (Western Washington.) 13. Ground color sufficiently dark to obscure dorsal spots; top of head mainly black. .Thamnophis sirtalis tetrataenia (Cope) (California except immediate coastal region as far south as the southern end of the San Joaquin Valley; eastern parts of Oregon and Washington ; Idaho and western Nevada.) Ground color paler, not entirely obscuring dorsal spots ; top of head mostly olive 14 14. Stripes broader, duller colored. Thamnophis sirtalis parietalis (Say) (Iowa and Minnesota, Missouri westward to Utah, eastern Nevada, southern Idaho; southern Alberta and Manitoba, Canada.) Stripes narrower and bright yellow. Thamnophis sirtalis infernalis (Blainville) (Coastal strip of California from Humboldt County to northern San Diego County.) 15. Dorsal stripe bright yellow and well developed 16 Dorsal stripe faint, discontinuous, or absent 19 16. 2 preoculars on one or both sides; scale rows 21, 22, or 23 when counted at a point one-third of the distance from head back to anus. Thamnophis ordinoides biscutatus (Cope) (Southern Oregon and northern California in the drain- age basins of the Klamath, Tide and Goose lakes.) 1 preocular ; scale rows 19, 20, or 21 when counted at a point one-third of the distance from head back to anus 17 17. Red markings often present on sides or on ventral surface; lateral stripes sometimes red ; head narrow ; ventrals usually less than 160. Thamnophis ordinoides atratus (Kennicott) (Coast region of northern California south to Santa Bar- bara County.) No red in coloration ; head wide and swollen ; ventrals usually more than 160 18 54 Bulletin 16: Zoological Society of San Diego 18. 19 scale rows; ground color of dorsolateral area brown; on each side two series of conspicuous dark spots which may invade the dorsal or lateral stripes ; posterior chin-shields markedly longer than anterior. . . .Thamnophis eques (Reuss) (Utah, Arizona, New Mexico and Texas, southward to Guatemala.) 21 (occasionally 20 or 19) scale rows ; ground color of dorso- lateral area nearly black, sufficiently dark nearly to obscure superimposed dark spots ; posterior chin-shields not much longer than anterior. Thamnophis ordinoides elegans (Baird and Girard) (Southwestern Oregon, northern California, Sierra Ne- vada slopes of Nevada and California and in the San Bernardino Mountains.) 19. Dorsal stripe absent 22 Dorsal stripe present but faint or confined to the anterior part of body 20 20. Dorsal stripe visible for full length of body, but faint, irreg- ular or invaded by small, rounded dorsal spots ; iris dark brown with narrow yellow rim around pupil. Thamnophis ordinoides vagrans (Baird and Girard) (Coastal region of British Columbia and Washington, and high Sierra Nevada of California, eastward to Alberta, Canada, South Dakota and Oklahoma.) Dorsal stripe faint, usually confined to anterior part of body ; dorsal surface checkered with large square-shaped mark- ings ; iris uniformly brown or gray 21 21. 21 scale rows, both in neck region and middle of body ; dorsal stripe often confined to neck region. Thamnophis ordinoides couchii (Kennicott) (Sacramento and San Joaquin Valleys in California, east- ward over the Sierra Nevada into Douglas and Washoe Counties, Nevada.) 19 scale rows, either in neck region, or middle of body, or both; dorsal stripe discernible at least on anterior half of body Thamnophis ordinoides hydro phila Fitch (Southwestern Oregon and northwestern California, from the Umpqua River in the north to the Gualala River in the south; east to the Shasta River and the Sacramento Val- ley.) 22. Lateral stripe well developed ; dorsal spots small and in- conspicuous Thamnophis hammondii (Kennicott) (Southwestern California and adjacent Lower California.) Perkins: A Ivey to the Snakes of the United States 55 Lateral stripe usually absent ; dorsal spots numerous and prominent Thamnophis angustirostris (Kennicott) (Southeastern Arizona and southwestern New Mexico south to Coahuila and Durango, Mexico.) Genus Trimorphodon * 1. Pattern consists of dark cross-bands, much narrower than the interspaces Trimorphodon vilkinsonii Cope (Extreme western Texas and Chihuahua, Mexico.) Pattern of dark blotches (each split by a light transverse line) equal to or greater in width than the interspaces. ... 2 2. Anal plate almost always divided; blotches 21 to 34. Trimorphodon lyrophanes (Cope) (Southwestern Utah, Arizona, southern Nevada, south- eastern California, central and southern Lower Cali- fornia and northwestern Mexico.) Anal plate almost never divided ; blotches 28 to 43. Trimorphodon vandenburghi Klauber (Los Angeles and Inyo Counties south throughout Cali- fornia to the Mexican border, but not including the country adjacent to the Colorado River.) Genus Tropidoclonion Tropidoclonion lineatum (Hallowed) (Ohio to Iowa and southeastern South Dakota and through Missouri, Kansas, and Arkansas to Oklahoma and Texas.) * Adapted from L. M. Klauber: The Lyre Snakes (Genus Trimorphodon) of the United States. Trans. S. D. Soc. Nat. Hist. Vol. 9, No. 19. April, 1940. 56 Bulletin 16: Zoological Society of San Diego , -SUPRAOCULAR PREOCULARS— • PIT — SUPRALA8IALS INFRAL ABIALS- -CANTHALS INTERNASAL -POSTNASAL - PRENASAL L- ROSTRAL -FIRST SUPRALABIAL MENTAL \ v GENIAL VF IRS T INFRALABIAL LOREALS CANTHALSV POST NASAL.. NOSTRIL-.. PRENASAI ROSTRAL- PIT— FIRST SUPRALABIAL MENTAL - FIRST INFRAL^BIAL" LOWER PREOCULAR' , UPPE R PREOCULAR 7 ^.SUPRAOCULAR ' , POSTOCULARS -LAST SUPRALABIAL — LAST INFRALABIAL CANTHUS ROSTRALIS- NOSTRIL— PREFRONTAL AREA (INTERCANTHALS) . FRONTAL AREA— (INTERSUPRAOCULARs) -ROST Ral. ..-INTERNASAL ..-PRENASAL —,-CANTHALS SUPRAOCULAI* MENTAL -FIRST INFRALABIALS . tvA*---.- S E N I ALS .->GUL ARS .-FIRST VENTRAL .-LAST INFRALABtAL -RICTUS OF MOUTN OR COMMISSURE VEHTRALfS OR GASt ROSTEGES Nomenclature of head scales — ( Crotalus ) Perkins: A Key to the Snakes of the United States 5 7 Method of counting dorsal scale rows. FRONTAL v SUPRAOCULAR v \ PREOCULAR. \ \ \ ' X PREFRONTAL s \ \ ' POSTNASALn \ \ \ L l! ! > /L ^ v ' 1 — 1/ v . POSTOCULARS / -PARIETAL / ‘ 1] J .FIRST TEMPORAL l'l / / / SECOND TEMPORALS I / J INTERNASAL-^ PRENASAL--^ ROSTRAL FIRST UPPER LABIAL — ' MENTAL'^" FIRST LOWER LABIAL LAST UPPER LABIAL — LAST LOWER LABIAL 'LOREAL Nomenclature of head scales — ( Lampropeltis ) 58 Bulletin 16: Zoological Society of San Diego GLOSSARY Anal plate. — The scale covering the anus; it may be either one large scale or divided into two scales by a diagonal or longitudinal slit. Apical scale-pits. — A pair (single in some snakes) of depressions faintly evident on the posterior end of each scale; usually most evident dorsally near the tail. Azygous scale. — A small plate behind the rostral, between the internasals. Body. — From head to anus. Body blotches. — These are counted from the posterior edge of the head to the anus. On the sides there are usually additional series of smaller blotches known as lateral or secondary blotches, often in several rows, one below the other. In many snakes, especially on the posterior half or third of the body, the main dorsal blotches merge with the laterals to form cross-bars or rings. Canthals. — In some snakes, the border scales of the crown between the internasals and the supraoculars. Canthus rostralis. — The outer edge of the flat area of the crown where it turns downward on the side, extending from the rostral to the supra- ocular. Caudals. — Large scales on the under-tail; in either two or one series. In the case of divided caudals each pair is counted as one. Also referred to as subcaudals or urosteges. Chin-shields. — Usually two pairs (anterior and posterior) of enlarged scales under the head between the two rows of lower labials. Frontal. — A large median plate on the top of the head between the supra- oculars. In some snakes this space is filled with scales more or less irregularly disposed and is referred to as the frontal area, and the scales as the intersupraoculars. Gastrosteges. — See ventrals. Genials. — See Chin-shields. Gulars. — The small scales covering the underside of the head between the two rows of lower labials and not otherwise specifically named. Head length. — The distance measured from the tip of the rostral to a line joining the posterior tips of the mandibular bones. Infralabials. — See labials, lower. Intercanthals. — In some snakes, the small irregularly disposed scales occupying the space anterior to the frontal area and between the canthals. Intergenials. — Small scales between the chin-shields. Internasals. — Usually two plates, in some snakes one, on top of the head just behind the rostral. In some rattlesnakes, three or more. Intersupraoculars. — See frontal. Keel. — A median longitudinal ridge on a scale. Labials, Lower. — Lip plates along the lower jaw on each side, separated in front by the mental. Perkins: A Key to the Snakes of the United States 59 Labials Upper. Lip plates along the upper jaw on each side, separated in front by the rostral. Length. The length over-all (or body length) is measured from the tip of the rostral to the end of the tail; in the rattlers, to the forward edge of the proximal rattle. Loreal. — One or more small scales between the preoculars and nasal. In case there are no preoculars, an elongated scale between the eye and the nasal. Mental. — The plate at the extreme anterior point of lower jaw. Nasal. If the nostril is in the center of a large scale, this scale is called the nasal. If the nostril lies between two scales, these are called the anterior and posterior nasal, or prenasal and postnasal. Parietals. — Paired large plates behind the frontal. Pit. — A deep depression on the side of the head below and behind the nostril and in front of the eye. Where pit-border scales are mentioned, those constituting the internal rim are meant, rather than those which are completely external to the pit. The pit is present only in the so- called pit vipers; represented in the United States by the rattlesnakes, copperheads and cotton-mouth moccasin. Postnasal. — See nasal. Postocular. — One or more small scales bordering the eye posteriorly. Postrostral. — See azygous scale. Prefrontals. — Paired (sometimes three or more) large plates immediately anterior to the frontal. Prenasal. — See nasal. Preocular. — One or more small scales bordering the eye in front. If such a scale is much longer than high and there is only one between the postnasal and eye, it is called a loreal, in which case the preocular is absent. Rattle. — The proximal rattle (or segment) is that next the tail. The button is the first permanent segment acquired by a baby rattlesnake; the pre- button or segment present at birth is invariably lost with the first exuviation. Rostral. — The plate at the extreme anterior point of snout. Scale formula. — A series of numbers representing the number of scale rows counted at different places on the body. Three numbers, say 17-19-15, would mean 17 scale rows at the anterior portion of the body, about a head length behind the head, a maximum of 19 scale rows near the middle of the body, and 15 scale rows at the posterior end a short distance anterior to the anus. A higher formula would mean more scale rows and a lower formula would mean less scale rows. Scale rows. — The number of rows of dorsal scales starting the count on the first row above the ventrals and continuing to the ventrals on the other side. Unless otherwise stated, the maximum number is given and can best be taken a little anterior to the middle of the body. Sex. — Dissection of under portion of tail, just posterior to the anus, will show, in a male, two organs (the hemipenes) and two scent glands; in the female the scent glands only will be shown. A male usually has a longer tail with a gradual taper, while a female has a shorter tail with a noticeable constriction at the anus. 60 Bulletin 16: Zoological Society of San Diego Subcaudals. — See caudals. Suboculars. — In some snakes, small scales between the eye and the upper labials. Supralabials. — See labials, upper. In Leptotyphlops the supralabials are named as follows: (1) nasal (or inferior nasal, if the nasal be divided); (2) an- terior supralabial; (3) ocular; (4) posterior supralabial. The anterior supralabial may be split vertically. Supraoculars. — Large scales above the eyes. Suture. — A division between two scales or plates, or the parts of a plate. Tail length. — Distance from anus to tip of tail. In rattlesnakes from anus to proximal rattle. Tail rings or blotches. — The dorsal rings or blotches between the anus and the tip of the tail or proximal rattle. Temporals. — Anterior temporals are large scales, one above the other, be- hind the postoculars and between the parietals and upper labials. Pos- terior temporals are similar scales behind the anterior temporals. Urosteges. — See caudals. Ventrals. — Large scales, transversly elongated, on the under surface from the under side of the head to the anal plate. To count the ventrals begin with the first scale that is transversely elongated and end with the scale anterior to the anal plate. Also referred to as gastrosteges. Perkins: A Key to the Snakes of the United States 61 INDEX abacura, Farancia abacura, 33 Abastor, 21, 16, 20, 6 abyssus, Crotalus viridis, 27 adamanteus, Crotalus, 28 aestivus, Opheodrys, 44 affinis, Pituophis sayi, 45 Agkistrodon, 21, 14, 11 alleni, Liodytes, 40 alerna, Lampropeltis, 35 amabilis, Diadophis amabilis, 31 amaura, Lampropeltis triangulum, 37, 38 amoena, Carphophis amoena, 22 angustirostris, Thamnophis, 55 annectens, Pituophis catenifer, 46 annulata Lampropeltis triangulum, 37 Arizona, 22, 18, 7 arizonae, Diadophis regalis, 30 arnyi, Diadophis punctatus, 30 atratus, Thamnophis ordinoides, 53 atricaudatus, Crotalus horridus, 29 atriceps, Tantilla, 51 atrox, Crotalus, 27 bairdi, Elaphe, 32 barbouri, Micrurus fulvius, 40 barbouri, Sistrurus miliarius, 48 biscutatus, Thamnophis ordinoides, 53 blanchardi, Sonora semiannulata, 49 bottae, Charina, 22 boylii, Lampropeltis getulus, 36 brooksi, Lampropeltis getulus, 36 browni, Heterodon contortrix, 34 browni, Phyllorhynchus browni, 44 Bull snake, 45 butleri, Thamnophis, 52 cahuilae, Leptotyphlops humilis, 40 California boa, 40 californiae, Lampropeltis getulus, 36 calligaster, Lampropeltis, 37 cana, Ficimia, 33 Carphophis, 22, 18, 6 catenatus, Sistrurus catenatus, 47 catenifer, Pituophis catenifer, 46 Cemophora, 22, 18, 8 cerastes, Crotalus, 25 Charina, 22, 15, 6 Chicken snake, 32 Chilomeniscus, 23, 19, 9 chlorosoma, Elaphe, 32 cinctus, Chilomeniscus, 23 clarkii, Natrix sipedon, 42 coccinea, Cemophora, 22 Coluber, 23, 18, 7 compressicauda, Natrix sipedon, 42 concinnus, Thamnophis sirtalis, 53 confinis, Elaphe obsoleta, 33 confluens, Natrix sipedon, 43 Coniophanes, 25, 20, 10 constrictor, Coluber constrictor, 23 Contia, 25, 19, 8 contortrix, Heterodon contortrix, 34 Copperhead, 21 Coral snake, 40 Corn snake, 32 coronata, Tantilla coronata, 50 Cotton mouth, 21 couchii, Thamnophis ordinoides, 54 couperi, Drymarchon corais, 31 Crotalus, 25, 15, 12 cupreus, Agkistrodon mokasen, 21 cyclopion, Natrix cyclopion, 42 deckerti, Elaphe quadrivittata, 33 decolor, Crotalus viridis, 27 dekayi, Storeria, 49 deppei, Pituophis deppei, 45 Desert boa, 40 deserticola, Pituophis catenifer, 46 Diadophis, 29, 18, 6 dissectus, Leptotyphlops dulcis, 39 Drymarchon, 31, 18, 7 Drymobius, 32, 17, 7 dulcis, Leptotyphlops dulcis, 39 edwardsii, Diadophis punctatus, 30 eiseni, Tantilla, 51 Elaphe, 32, 17, 20, 7 elapsoides, Lampropeltis elapsoides, 38 elegans, Arizona elegans, 22 elegans, Haldea valeriae, 34 elegans, Thamnophis ordinoides, 54 episcopa, Sonora, 48 eques, Thamnophis, 54 erythrogaster, Natrix erythrogaster, 42, 43 ervthrogrammus, Abastor, 21 euryxanthus, Micruroides, 40 extenuatum, Stilosoma, 49 Farancia, 33, 16, 20, 6 fasciata, Natrix sipedon, 44 Ficimia, 33, 19, 9 flagellum, Coluber flagellum, 24, 25 flavigularis, Coluber flagellum, 24, 25 flavilata, Rhadinaea, 46 flaviventris, Coluber constrictor, 23 floridana, Lampropeltis getulus, 36 floridana, Natrix cyclopion, 42 Fox snake, 32 frenatum, Coluber flagellum, 24 fulvius, Micrurus fulvius, 41 Garter snake, 51 gentilis, Lampropeltis triangulum, 38 getulus, Lampropeltis getulus, 36 62 Bulletin 16 : Zoological Society of San Diego girardi, Coluber taeniatus, 24 gloydi, Sonora semiannulata, 49 Gopher snake, 45, 31 gracia, Lichanura roseofusca, 40 gracilis, Tantilla, 50 grahamiae, Salvadora grahamiae, 46 grahamii, Natrix, 41 Green snake, 44 Ground rattler, 47 guttata, Elaphe, 32 Haldea, 34, 16, 17, 18,9 hammondii, Thamnophis, 54 helenae, Carphophis amoena, 22 Heterodon, 34, 16, 6 hexalepis, Salvadora grahamiae, 47 Hog-nose snake, 34 holbrooki, Lampropeltis getulus, 35 Horn snake, 33 horridus, Crotalus horridus, 29 luimilis, Leptotyphlops humilis, 40 hydrophila, Thamnophis ordinoides,54 Hypsiglena, 35, 20, 10 imperialis, Coniophanes imperialis, 25 Indigo snake, 31 infernalis, Thamnophis sirtalis, 53 insularum, Natrix sipedon, 42 kennerlyi, Heterodon nasicus, 34 King snake, 35 kirnia, Tantilla, 51 kirtlandii, Natrix, 41 klauberi, Crotalus lepidus, 26 laeta, Elaphe, 32 Lampropeltis, 35, 18, 8 lateralis, Coluber, 24 laticinctus, Agkistrodon mokasen, 21 Leaf-nosed snake, 44 lecontei, Rhinocheilus, 46 lepidus, Crotalus lepidus, 26 Leptodeira, 39, 20, 10 Leptotyphlops, 39, 14, 6 Lichanura, 40, 15, 6 linearis, Sonora miniata, 49 lineatum, Tropidoclonion, 55 Liodytes, 40, 16, 10 lodingi, Pituophis, 46 lucidus, Phyllorhynchus browni, 44 lutosus, Crotalus viridis, 28 Lyre snake, 55 lvrophanes, Trimorphodon, 55 marcianus, Thamnophis, 52 margaritiferus, Drymobius, 32 Massasauga, 47 megalops, Thamnophis, 52 melanoleucus, Pituophis, 45 melanurus, Drymarchon corais, 31 microphthalmus, Oxybelis, 44 Micruroides, 40, 19, 1 1 Micrurus, 40, 19, 1 1 miliarius, Sistrurus miliarius, 48 Milk snake, 35 miniata, Sonora miniata, 49 modestus, Diadophis amabilis, 30 mokasen, Agkistrodon mokasen, 21 molossus, Crotalus molossus, 29 mormon, Coluber constrictor, 23 mugitus, Pituophis, 46 multicincta, Lampropeltis, 37 nasicus, Heterodon nasicus, 34 Natrix, 41, 17, 9 nigra, Lampropeltis getulus, 35 nigriceps, Tantilla, 51 nubilus, Phyllorhynchus decurtatus, 45 nuntius, Crotalus viridis, 27 obsoleta, Elaphe obsoleta, 33 occidentalis, Arizona elegans, 22 occidentalis, Diadophis amabilis, 31 occipitalis, Sonora, 48 occipitomaculata, Storeria, 49 ochrorhynchus, Hypsiglena, 35 Opheodrys, 44, 17, 18, 7 ordinoides, Thamnophis ordinoides, 52 oreganus, Crotalus viridis, 28 Oxybelis, 44, 19, 10 parietalis, Thamnophis sirtalis, 53 Patch-nosed snake, 46 perkinsi, Phyllorhynchus decurtatus, 45 Phyllorhynchus, 44, 17, 18, 7 piceus, Coluber, 24 pickeringii, Thamnophis sirtalis, 53 pictiventris, Natrix sipedon, 44 Pilot black snake, 33 Pine snake, 45 piscivorus, Agkistrodon, 21 Pituophis, 45, 17, 8 pleuralis, Natrix sipedon, 43 priapus, Coluber constrictor, 23 pricei, Crotalus triseriatus, 29 proximus, Thamnophis sauritus, 51 pulchellus, Diadophis amabilis, 31 punctatus Diadophis punctatus, 30 pygaea, Seminatrix, 47 pyromelana, Lampropeltis, 37 pyrrhus, Crotalus mitchellii, 26 quadrivittata, Elaphe quadrivittata, 33 Racer, 23 radix, Thamnophis, 52 Rainbow snake, 21 Rat snake, 32 Rattlesnake, 25, 47 regalis, Diadophis regalis, 30 reinwardtii, Farancia abacura, 33 Perkins : A Ivey to the Snakes of the United States 63 Rhadinaea, 46, 19, 6 Rhinocheilus, 46, 17, 8 rhombifera, Natrix rhombifera, 42 rhombomaculata, Lampropeltis, 37 Ribbon snake, 51 rigida, Natrix, 41 Ring-neck snake, 29 rosacea, Elaphe, 32 roseofusca, Lichanura roseofusca, 40 Rough green snake, 44 Rubber snake, 22 ruber, Crotalus, 27 rutbveni, Coluber taeniatus, 24 ruthveni, Pituopbis, 45 sackenii, Thamnophis sauritus, 51 Salvadora, 46, 18, 7 sauritus, Thamnophis sauritus, 51 sayi, Pituopbis sayi, 45 schotti, Coluber taeniatus, 24 scutulatus, Crotalus' scutulatus, 27, 29 segregus, Leptotyphlops humilis, 39 semiannulata, Sonora semiannulata, 49 semilineatus, Coluber, 24 Seminatrix, 47, 17, 19, 9 septemvittata, Natrix, 41 septentrionalis, Leptodeira septentrionalis, 39 Sidewinder, 25 similis, Diadophis amabilis, 31 simus', Heterodon, 34 sipedon, Natrix sipedon, 43 sirtalis, Thamnophis sirtalis, 52 Sistrurus, 47, 14, 11 Smooth green snake, 44 Sonora, 48, 19, 9 splendida, Lampropeltis getulus, 35 Spreading adder, 34 stephensi, Crotalus mitchellii, 28 stictogenys, Diadophis punctatus, 30 Stilosoma, 49, 18, 8 Storeria, 49, 16, 9 streckeri, Fieimia, 33 streckeri, Sistrurus miliarius, 48 striatula, Haldea, 34 subocularis, Elaphe, 32 syspila, Lampropeltis triangulum, 39 taeniatus, Coluber taeniatus, 24 Tantiila, 50, 19, 11 taxispilota, Natrix, 41 taylori, Sonora, 48 tenere, Micrurus fulvius, 41 tenuis', Contia, 25 tergeminus, Sistrurus catenatus, 47 tetrataenia, Thamnophis sirtalis, 53 Thamnophis, 51, 17, 10 tigris, Crotalus, 28 transversa, Natrix erythrogaster, 43 triangulum, Lampropeltis triangulum, 38 Trimorphodon, 55, 18, 20, 10 Tropidoclonion, 55, 17, 10 utahensis, Leptotyphlops humilis, 39 utahensis, Tantiila, 51 vagrans, Thamnophis ordinoides, 54 valeriae, Haldea valeriae, 34 vandenburghi, Diadophis amabilis, 31 vandenburghi, Trimorphodon, 55 vermis, Carphophis amoena, 22 vernalis, Opheodrys, 44 victa, Storeria, 49 vilkinsonii, Trimorphodon, 55 virginiana, Lampropeltis elapsoides, 38 virgultea, Salvadora grahamiae, 47 viridis, Crotalus viridis, 27 vulpina, Elaphe, 32 wagneri, Tantiila coronata, 50, 51 Water moccasin, 21 Water snake, 41 Whip snake, 23 wilcoxi, Tantiila, 50 willardi, Crotalus, 25 Worm snake, 39, 22 yumensis, Lampropeltis getulus, 36