CROCODITJANS, LIZARDS, AND SNAKES. 035 



sides, juid rarely the postoculars may be fused, and two superior 

 labials may be eijually rarely fused. According to Giiuther and Bou- 

 leuger the forms witli interuasal plates are only variations of this 

 species, and the form of the rostral may vary from obtusely rounded 

 to angulate, and to angulate with concave superior surfaces. That 

 this incredible raiige of variations is characteristic of this species is 

 sustained by the existence, according to these authors, of two individ- 

 uals in the British Museum in which the internasal is present on one 

 side and absent on the other. The great majority of specimens are, 

 however, according to these authors, constant in these respects. Thus 

 Boulenger enumerates thirteen individuals with iuternasals present on 

 both sides and sixteen in which they are absent on both sides. Under 

 such circumstances the irregularity in question would seem to be 

 rather an anomaly than an indication that all the specimens belong to 

 one species. This view is confirmed by ten specimens at my disposal 

 which come under the definition of Conojjsis nasus as given by Boulen- 

 ger. Five, which I refer to the C. nasus, constantly lack iuternasals, 

 and five which 1 refer to Toluca Kneata, Chionactis diasii, and Chionactis 

 varians, as constantly possess them. All possess loreals except the two 

 individuals of Toluca lineata, where the nasal articulates with the pre- 

 ocular; and one side of two individuals of Conopsis nasus, where, on 

 the contrary, the nasal terminates posteriorly in an acute angle, not 

 reaching the x^reocular. 



The small black dorsal spots are obsolete in four of the five specimens 

 before me. These were sent me by M. Boucard, of Paris, without 

 especial indication of locality. 



Duges gives as habitats of this species the valley of Mexico, Leon, 

 Guanajuato, and Zacatecas. 



CHIONACTIS Cope. 



Chionactis CoPB,Froc. Acad. Nat. Sci. Phila., 1861, p. .S03; Check-list N. Amer. 



Uatr. Kept., 1875, p. 35; Bull. U.S.Nat. Mus., No. 32, 1887, p. 53 ; I'roc U. S. 



Nat. Mus., XIV, 1892, p. 604. 

 Lamprosoma Hallowki.l, Proc. Acad. Nat. Sci. Pliila., 1856, p. 310; Reiitilea Surv. , 



U. S. Pac. R. R., X, 1859, Williamson's Report, p. 15. 

 Ogmiiis Cope, Proc. Amor. Phil. Soc, 1869, p. 162. — Boulengek, Cat. Snakes 



Brit. Mus., 2d ed., Ill, 1896, p. 228. 

 Oxyrliitia Jan, Arcli. Zool. Anat. Phys., II, 1862, p. 59; not of Agassiz. 



Posterior maxillary (ooth not enlarged, with a shallow external 

 sulcus. iSTasal plate single, pierced by the nostril, distinct from ihe 

 labials. Iuternasals and preocular present. Anal and subcaudal 

 plates double. Loreal usually i)resent. 



This genus tends to Stenor}ii)i((, from Avhich it differs in the distinct- 

 ness of the nasal plate from those adjacent, and more widel}^ in the 

 calyculate character of the hemipenis. From Cono2>s>s it differs only 

 in the presence of internasal plates. The last maxillary tooth is only 

 moderately enlarged, and the groove is on the external face and is not 



