16 PROCEEDINGS OF THE ACADEMY OF 



breadth. One inch from the head six segments occupied the space 

 of a line ; at the posterior part of the bod}' four segments occu- 

 pied the same extent. The species appeal's not to have been pre- 

 viously described, and may, therefore, be named Taenia bipapil- 

 losa. 



The Extinct Batrachia of Ohio. Prof. Cope stated that the 

 explorations of the coal measures in eastern Ohio conducted 

 during the past season by Prof. Newberry, State Geologist, had in- 

 creased the number of species of extinct Batrachians to thirty-three. 

 A new genus and species were described under the name of Pleu- 

 roptyx clavatus, which is remarkable for the structure of its ribs. 

 Each of these presents a wide thin ala on its posterior face, which 

 is abruptly discontinued below. The shaft of the rib is short and 

 enlarged distally, where it is hollow and truncate. The vertebras 

 are as large as those of the anaconda, and there is no ventral 

 armature preserved. Another genus exhibits two strata of chev- 

 rons in an armature of ventral rods, the angle of the upper having 

 an opposite direction to that of the lower. The gular scuta are 

 smooth. It was named Hyphasma Isevis. An interesting addition 

 to the fauna was stated to be a new species of the horned genus 

 Ceraterpeton, Huxl. The head is relatively large, and covered 

 witli recticulate ridges separated by rows of impressed dots. 

 Horns long, stout, and incurved. It was called C.punctolineatum. 



Prof. Persifor Frazer, Jr., exhibited a combination of the 

 polarizer, vertical lantern, and microscope, by means of which the 

 manner in which different salts crystallized out of their solutions, 

 together with the manner in which the}' affect polarized light, was 

 explained and illustrated by solutions of potassium chlorate and 

 urea in alcohol. The light from a lime lantern is passed tli rough 

 the elbow-tube polarizer, thence upward through the vertical lantern 

 and the two-inch lens microscope, when it is again reflected hori- 

 zontally on the screen. After the formation of the crystals had 

 been shown by plain polarized light, the analyzer was inserted and 

 the characteristic colors of polarization produced. It was ex- 

 plained that while this method had the advantage of so magnify- 

 ing the crystals produced from small quantities of solutions that 

 their structure could be minutely observed, as well as the sudden 

 molecular change which caused the polarizing effect, it was open 

 to the objection of a very large loss of light first, by the polar- 

 izer, and again by the microscope. It was suggested that a means 

 of obviating at least a part of this difficulty would be the use of 

 the parabolic reflector, in connection with the first condenser. 



Prof. Frazer then proceeded to exhibit the microscopic structure 

 of thin sections of some of the Palaeozoic rocks found in York and 

 Adams Counties, Pa. A map of the region whence the specimens 

 were collected was first thrown on the screen and the geological 



