Miscellaneous. 389 
Anew Form of Freshwater Sponge. 
A note was read from Mr. Edward Potts, reporting the discovery 
in Chester Creek of another curious form of freshwater sponge, a 
third species of Oarterella, resembling C. tubisperma in the character 
of its birotulates and the length of its foraminal tubes, but much 
more robust than that species. The tendrils are nearly as long as 
those of C. tenosperma, but broad, flat, and riband-like. 
Thus far it is the most conspicuous and peculiar of our American 
forms. He proposed for it the name OCarterella latitenta.—Proc. 
Acad. Nat. Sci. Philad., July 26, 1881, p. 176. 
Note on the Structure of the Posterior Foot of Toxodon. 
By E. D. Copz. 
The position of the genus Yowodon in the system of Mam- 
malia is a question upon which few authorities have expressed 
positive opinions, and which is generally regarded as still an open 
question. In the lack of certainty on the subject, a separate order, 
the ‘‘Toxodontia,” has been proposed for its reception. It is known 
that the genus is ungulate, but the opinions of authors are much 
divided as to its relations to the three principal orders included 
under that head. Resemblances to the Proboscidea have been de- 
tected; but Prof. Gervais (‘Comptes Rendus,’ 1878) asserts that 
there is a close resemblance to the genus Hippopotamus in the struc- 
ture of the posterior foot. 
Haying come into possession of remains of Zoaodon, which include 
the greater part of the skeleton, I make a few observations on the 
affinities suggested by the posterior foot, the only portion just now 
accessible in my collection. The calecaneum and astragalus have 
been more or less imperfectly figured by De Blainville and Bur- 
meister, but no one has, to my knowledge, represented the entire 
foot. The caleaneum is rather short and stout and its external 
convex tuberosity is of unusual size. Its articular surface is divided 
into two subequal parts, the internal of which supports the astra- 
galus, the external the fibula. Thus the fibular articulation is of 
unusual size. The cuboid facet is on the inferior face of the extre- 
mity of the caleaneum, thus looking directly downwards when the 
bone is prone. In order to articulate with the remainder of the 
foot, the caleaneum must have been inclined upwards and forwards 
at an angle of 45°, and the cuboid inclined downwards and for- 
wards at a similar angle. That the axis of the astragalus had the 
latter inclination is proven by the fact that the superior plane of 
the sustentaculum lies at that angle to the axis of the remainder of 
the calcaneum. The great convexity of the external tuberosity for 
the astragalus will also permit of such a position for the astragalus. 
The navicular facet of the astragalus is plane and truncates the bone 
somewhat inferiorly as well as distally, so as to present in the same 
way as the cuboid. There is probably no cuboid facet. I have not 
seen the cuneiform bones. The metatarsals and phalanges are 
Ann. & Mag. N. Hist. Ser. 5. Vol. viii. 27 
