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, the 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 vertebre 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, Pl. 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 vertebre 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. 13, 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 contortriz, 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 
