Brinton.] iJ4: [Jan. 2, 



dorsolateral brown band has a row of small dusky spots along its superior 

 and inferior edges. 



This species is near the H. infrataniatus Jan., and future investigation 

 may prove it to be a variety of that species. In two specimens of the 

 latter the scales are in seventeen rows, in three specimens of tlie H. halio- 

 gaster they are in nineteen rows. In a small H. infratceniatus the external 

 edges of the dorsal band are not spotted but form a dark band. The celor 

 of the lower surface in the two species is quite different. 



I note here that the Helicops alleni Garman, from Florida, has the scales 

 entirely smooth. It is necessary therefore that it be placed in another 

 genus, which I call Liodytes. Its diagnosis is that of Helicops with the 

 addition, scales smooth. 

 Elaps altirostris Cope. Three specimens. 

 BoTHROPS ALTERNATus D. & B. Commoh. 



Explanation of Plate. 



Heads and tails of Amphisbfenida^. Fig. a Head, from above ; 6, from 

 below ; c, from the side ; d, the tail with preanal plates and pores, from 

 below. 



Fig. 1. AmpMshcena trachura Cope. 



Fig. 3. AmpMshmna beniensis Cope. 



Fig. 3. Amphisbmna occidentalis Cope. 



Fig. 4. ArnpMsbcena angustifrons Cope. 



Fig. 5. AporarcJms prunicolor Cope. 



Fig. 6. AmphisboRna alba Linn (Three specimens). 



Fig. 7. A. alba var. radiata Cope. Caudal annuli 18 ; of the body 

 236 ; preanal plates 12 ; pores 8. Uniform white. Habitat unknown. One 

 specimen. 



Fig. 8. A. alba var. dissecta Cope. Annuli to vent 236 ; of tail 18 ; pre- 

 anal plates 12 ; pores 8. Brownish above, below white. Venezuela. One 

 specimen. 



The Lineal Measures of the Semi- Givilized Nations of Mexico and Central 

 America. By Daniel O. Brinton, M.J). 



[Read before the American Philosophical Society, January 2, 1SS5.) 



Positive progress in constructive art can be accurately esti- 

 mated by the kind and perfection of the instruments of pre- 

 cision employed by the artists. A coi'rect theory of architecture 

 or of sculpture must have as its foimdation a correct system of 

 weights and measures, and recognized units and standards of 

 gravity and extension. Where these are not found, all is guess- 

 work, and a more or less hap-hazard rule-of-thumb. 



