404 ON A NEW SPECIES OF MACRAUCHENIA (M. BOLIVIENSIS) 
M, Patachonica, discovered by Mr. Darwin, and described by Professor 
Owen in the ‘Appendix to the Voyage of the Beagle’; and as, in 
addition, these and the other bones present different proportions from 
those of the Patagonian species, I have no hesitation in regarding the 
fossils collected by Mr. Forbes as the remains of a distinct species, 
for which I propose the name of JZacrauchenta Boliviensis. It will 
be convenient to commence the description of these fossils with those 
parts upon which the diagnosis of the species may be most safely 
rested, viz. the cervical vertebra and the astragalus. 
The cervical vertebra (Plate VI. [Plate 32.] fig. 1)—The great 
length of the centrum of this vertebra, the peculiar form of its 
transverse processes, and the absence of perforations for the vertebral 
arteries in them are characters which, in the present state of know- 
ledge, oblige the anatomist at once to refer it either to one of the 
existing Camelide or to the genus J/acrauchenia; while the two 
strong, converging ridges which mark the posterior half of the under 
surface of the vertebra, and meet to form a single ridge, which dies 
away anteriorly in the middle of that surface, together with the slight 
concavity of both the posterior and the anterior articular faces of the 
centrum, are decisive in favour of the latter alternative. In fact, the 
excellent description of the cervical vertebre of Macrauchenta Pata- 
chontca which has been given by Professor Owen applies so well to 
that of AZ. Boliviensis, that referring to the paper in the ‘ Appendix 
to the Voyage of the Beagle,’ already cited, for a general account of 
the characters of Macrauchenian vertebre, I shall content myself with 
pointing out the resemblances and differences of the Bolivian from 
the Patagonian J/acrauchenia, and from the existing duchenze. The 
dimensions of the centrum of the cervical vertebre of the two 
Macrauchente, and of the fourth cervical of a Guanaco and of a 
Vicugna in the College of Surgeons’ Museum are as follows :— 
AL. Boliviensts. AL, Patachontca. Guanaco. Vicugna. 
in. in. in. in. 
Length . obs » BS 66 46 40 
Width of anterior face. II 33 I'l 8 
Width of posterior face 1°25 34 1°3 ie) 
Thus it appears that the centrum of the cervical vertebra of 
Macrauchenia Poliviensts is far more slender than that of JAZ. Pata- 
chonica; for, while the length of the former is to that of the latter 
as 1:17, the transverse diameters of the anterior faces of the centra of 
the two species are, nearly, as 1:3. The cervical vertebra of the new 
species is, absolutely, rather shorter than the fourth cervical of the 
