Fig. 1. Left side of skull, incisors, canine, and premolars × 11, and occlusal surface of left first upper molar × 20. A. Myotis nigricans dalquesti, holotype. B. Myotis nigricans extremus No. 77674 USNM, topotype.
Remarks.—The subspecific name dalquesti is given in recognition of Prof. Walter W. Dalquest who gathered the largest and most varied collection of mammals ever taken in the state of Veracruz.
Inspection of the measurements given above will reveal that there is no overlap between extremus and dalquesti in the interorbital constriction or occipital depth and only slight overlap in the length of the maxillary tooth-row and maxillary breadth.
In 10 adult females from Ocosingo, Chiapas, there is suggestion of intergradation between dalquesti and extremus in that one specimen (66515 KU) has the cranial characters of extremus except that it is large like dalquesti; in two other skulls P3 is slightly displaced lingually and two other skulls bear a slight sagittal crest. These are features characterizing extremus. Otherwise the specimens resemble dalquesti, to which subspecies they are here referred.
Three males from a place 8 km. W and 10 km. N El Encino, 400 ft., Tamaulipas, are the northernmost representatives of the species and differ from the other specimens of dalquesti in shorter forearm, shorter maxillary tooth-row and lesser maxillary breadth.
Study in the laboratory was supported by Grant No. 56 G 103 from the National Science Foundation. Field work was supported by a grant from the Kansas University Endowment Association. We thank Dr. David H. Johnson for lending eight topotypes of M. n. extremus. Other specimens of extremus available to us are as follows: 1 mi. E Teapa, Tabasco, 1 (7535 LSU—courtesy of Dr. George H. Lowery, Jr.); Cayo Dist. Augustine, British Honduras, 1 (9670 KU, in red phase); 12 km. NNW Chinajá, Guatemala, 4.
Specimens examined.—Total, 142, as follows: Tamaulipas: 8 km. W, 10 km. N El Encino, 400 ft., 5. Veracruz: 4 km. WNW Fortín, 3200 ft., 1; 2 km. N Motzorongo, 1500 ft., 1; 3 km. E San Andrés Tuxtla, 1000 ft., 7; 38 km. SE Jesús Carranza, 500 ft., 118. Chiapas: Ocosingo, 10.
Transmitted June 30, 1961.
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