Crenshaw and Hopkins showed that asper did not intergrade with ferox.
The specimen from Chanquejelve is an intergrade between the two subspecies just mentioned.
For the present it seems best to regard the specimen merely as an intergrade.
The two subspecies of the Violet-green Swallow, thalassina and lepida, intergrade in Coahuila.
Previously the two kinds were thought not to intergrade and were regarded as two species.
The subspecies cahooni and compositus of the Brown-throated Wren seem to intergrade in the southern part of the State.
They intergrade with trumbullensis in the size and shape of the zygomatic arches and tympanic bullae.
Since neomexicana and arizonensis intergrade it is probable that nevadensis also will be found to intergrade with neomexicana.
Also, Dipodomys oklahomae was not known to intergrade with any other named kinds.
Where the ranges of the two species meet in Washington they seem not to intergrade.