Dr. H. Burmeister on Giyptodon and its Allies. 303 
I. Guiyrropon. 
Tail elongated, conical, the rings before the apex formed of 
flat shields or scales, the apex more or less cylindrical, with a 
bulbous swelling at its commencement. Mesocervical bone with 
five united vertebre. 
A. Scales or shields of the carapace with uniform warty sculp- 
ture, only the marginal row of the carapace before the mar- 
ginal tubercles with an elliptical rosette. 
1. G. tuberculatus, Owen, Nodot. 
2. G. verrucosus, Nodot (G. tuberculatus, nob.,.in former com- 
munication), 
B. Scales or shields of the carapace with a central subhexagonal 
rosette, and six smaller subpentagonal ones on the circum- 
ference; the scales of the margin of the carapace before the 
marginal tubercles with a very large central rosette, occu- 
pying nearly the whole shield. 
3 & 4. G. clavipes auctorum. 
Note.—We have in the Museum two different kinds of tails,— 
the one shorter, broader, and flatter, with an elliptical transverse 
section; the other longer, thinner, and higher, with a more cir- 
cular section. I believe they belong to two different species ; 
but as I do not know the exact form of the tail of Professor 
Owen’s G. clavipes, I must leave it doubtful which of my species 
is the true clavipes. 
Il. Hortornorvs, Lund. 
Schistopleurum, Nodot. 
Tail short, conical, with six rings of large conical tubercles on 
the end of each ring of the upper side of the tail*. Mesocervi- 
cal bone consisting of four united vertebra, the sixth free. Scales 
of the carapace with one hexagonal figure m the centre, and six 
pentagonal ones on the circumference. 
5. H. elongatus, nob. (Schistopleurum typus, Nodot). 
6. H. gemmatus, nob. (S. gemmatum, Nodot). 
7. H. asper, nob. (G. spinicaudus, nob. anted). 
8. H. pumilio, nob., Anales del Museo publico de Buenos 
Aires, i. p. 77. Of this last species I know only the lower jaw, 
but, from its general figure, I suppose the species to belong to 
this section. 
* As we have in the Museum a well-preserved tail of the species which 
has been described by Nodot as S. typus, with moveable central tubercles 
on the rings, I can affirm that this construction is not natural, but caused 
by the imperfect healing of the broken tubercles during the life of the 
animal. This process is denominated in surgery artificial articulation. 
