A new water snake from Mexico, with notes on anal plates and apical pits in Natrix and Thamnophis. American Museum novitates ; no. 2060

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New York, N.Y. : American Museum of Natural History
"A new striped race of the Mexican west coast water snake, which bears a remarkable resemblance to a garter snake (Thamnophis), is diagnosed and described as Natrix valida thamnophisoides. Populations of this form are the only members of the species complex known to occur at fairly high elevations. Their distribution is compared with the ranges of the lowland populations, and intergradation between thamnophisoides and subspecies valida is discussed. It is shown that paired apical pits occur on the dorsal scales, especially of the nuchal region, in many Thamnophis, thus refuting the statement of several authorities that such pits are absent in all garter snakes. It is also shown that pits may be absent in some water snakes, especially in the Natrix valida complex. The condition of the anal plate, whether single or divided, although widely used in keys for the separation of the genera Natrix and Thamnophis, also varies, at least in a few species"--P. 20-21.
22 p. : ill. ; 24 cm.
Includes bibliographical references (p. 21-22).