Several features distinguish it from the _I. ohiensis_, one of which is of more than usual value if correctly indicated by the fossil. There are 10 vertebræ from the anterior end to the sacrum preserved in place, and none of them supports a rib, nor are there any ribs visible anywhere on the block of shale. I suspect that they exist on more anterior vertebræ, or may have been displaced to a more anterior position than they normally occupy. The abdominal chevrons are more anterior in position than are those of the _I. ohiensis_. The hind legs are longer than in that species; in this one the femur equals 7.5 vertebral centra in length. The external digit, on the other hand, while bearing 5 phalanges, is distinctly shorter. The fibular tarsal is of a transverse oval, not quadrate, form. The dorsal centra are shorter and deeper than long; the neural arches are elevated, with short but distinct zygapophyses, and a flat, subquadrate, superiorly truncate, neural spine. They bear short, vertically compressed diapophyses near the base of the arches. The neural spines of the caudal vertebræ become rapidly more slender, and also diminish in length, while the zygapophyses are continued to the fifteenth vertebra. The chevron bones are slender, and inclose a moderate hæmal opening. [Illustration: MOODIE PLATE 24 1. Photograph of the type specimen of _Pelion lyelli_ Wyman, from the Ohio Coal Measures. Supposed to represent the ancestral form of the Salientia. × 2. Original in American Museum of Natural History. 2. Scales of _Cercariomorphus parvisquamis_ Cope, a microsaur from the Ohio Coal Measures. × 10. Original in American Museum of Natural History. 3. Type specimen of _Cercariomorphus parvisquamis_ Cope, from the Ohio Coal Measures. Original in American Museum of Natural History. × 0.75. ]