MUSEUM OF COMPARATIVE ZOOLOGY 265 



the anterior of the three being partly subtended. In front of it, the 

 column is normal. Each vertebra is long, low, rather broad, and verti- 

 cally crossed in the middle by a light line, as if two had joined end to 

 end. The neural spines are low, inclined backward, and, in the hinder 

 three or four, expanded laterally on the upper edge into a flange that in 

 the posterior unites with the terminal bone. Zygapophyses and para- 

 pophyses are feebly developed ; the hypapophyses are blade-like, thin, 

 and fragile. Appearances suggest that the tip is carried upon and 

 struck against the ground. 



On Lachesis mutus, Linn., Fig. 11, from Brazil and Northern South 

 America, Vtie end of the tail is a long, slender, compressed, cultriform 

 blade. The scales in front of it are small and tubercular. This is es- 

 pecially the case with a dozen or more of the sub-caudals, that, as they 

 approach the end, are subdivided and spine-like. Within the cap the 

 bone is similar to those described above. The vertebrse preceding it are 

 slender, with weak processes. Near the extremity the tail is slender 

 and very flexible, a condition enhanced by the smallness of the scales. 

 It looks as if it were carried off the surface. 



Halys acutus, Gth., Fig. 12, is a serpent recently described by Dr. 

 Gunther, 1888 (Ann. Mag. Nat. Hist., (6), I. 171, PI. XII.), from the 

 mountains north of Kiu Kiang, China. It is remarkable on account 

 of a flexible pointed lobe extended from the end of the snout, and for 

 the peculiar scutellation of its compressed - tail. Dr. Gunther says the 

 tail is not to be in any way taken as an initial step in the develop- 

 ment of the rattle of Crotalus, though the organ in this species may in 

 a much smaller degree exercise the same function as in the rattlesnake, 

 being an instrument by which vibrations and sound are produced. 

 From what we have seen above, it is not difficult to imagine a rattle 

 developed from the arrangement of scales and vertebrse present in this 

 snake. However, as Dr. Gunther remarks, and as illustrated below, 

 it is quite unnecessary to suppose the tail of Crotalus has gone through 

 such modification.' 



Ancistrodon piscivorus, Holbr., Fig. 1 3, the Moccasin, from the South- 

 ern United States, is similar to Rhinocerophis in the structure of the 

 tip. The terminal bone is not so greatly developed. A greater number 

 of scales have fused with the cap. 



On Ancistrodon contor-trix, Linn., Fig. 14, the Copperhead, of the United 

 States to Mexico, the tip differs a little from that of its congener, the 

 Moccasin ; it is directed downward as well as backward. Most often 

 the cap, or button, has one or two swellings in a degree resembling those 



