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POPULAR SCIENCE REVIEW. 
Pterichthys with Astei'olepis and Heterostius ; and more especially because it 
shows a relationship to exist between these peculiar fishes and the anomalous 
living Lepidosiren, and thus showing that probably a parallel line ran 
upward from the Devonian Placodenus to the other living branch of the 
Dipnoan family, now represented by Lepidosiren and Protopterus. 
A new Trilobite. — Dr. S. T. Barrett has described, in the “American 
Journal of Science ” (March 1876), a new and interesting form of Trilobite, 
Dalmanites dentata , so named from the peculiar dentate margin of the 
cephalic shield. Each thoracic segment terminates with a slender terete 
spine, curved outward and backward. This species is found in the Lower 
Helderberg formation, near Port Jervis, Orange County. Some of the layers 
of the rock are mainly made of its remains. 
On a Gigantic Bird from the Eocene of New Mexico. — Professor Cope 
exhibited recently to the Philadelphia Academy of Science a tarsometatarsus 
of a bird, discovered by himself during the explorations in New Mexico, 
conducted by Lieutenant G. M. Wheeler, U. S. A. The characters of its 
proximal extremity resemble in many points those of the order Cursores 
(represented by the Struthionidce and JDinornis), while those of the distal 
end are, in the middle and inner trochlem, like those of the Gastornis of the 
Paris Basin. Its size indicates a species with feet twice the bulk of those 
of the ostrich. The discovery introduces this group of birds to the known 
faunae of North America, recent and extinct, and demonstrates that this 
continent has not been destitute of the gigantic forms of birds, heretofore 
chiefly found in the Southern Hemisphere faunae. 
MEDICAL SCIENCE. 
The Physiology of Hearing. — The “Berlin Journal of Chemistry” is 
responsible for the following facts, which it gathers from a medical journal. 
It states that Herr Urbantschitch calls attention to the fact that if a watch 
be held at a little distance from the ear, the ticking is not heard uniformly, 
but there is a swelling and diminishing of the sound. If held at such a dis- 
tance as to be scarcely audible, the ticking will come and go, being at times 
perceived distinctly, but at times becoming wholly inaudible, as if the 
watch were being moved to and from the ear. This variation in perception 
is not always gradual ; it is sometimes sudden. The same holds good for 
other weak sounds, as that of a weak water-jet, or a tuning-fork. Since 
breathing and pulsation have not the least influence on the phenomenon, the 
interruptions of the sensation must be attributed to the organ of hearing 
itself ; our ear is unable to feel weak acoustic stimuli uniformly, but has 
varying times of fatigue. To decide finally where the peculiarity lay, M. 
Urbantschitch made both ear-passages air-tight and applied a tuning-fork and 
a watch to the head. The sounds seemed not continuous, but intermittent. 
The cause must therefore be in the nerves of hearing. 
The Filtration of Typhoid Germs. — An important letter on this subject, 
with the general terms of which we entirely agree, has been published in 
the “ Sanitary Record,” June 3. Dr. Tripe calls attention to the statements 
