Hitherto only two portions of the dorsal series and a left limb have been assigned to this species. The present specimen (No. 4479, U. S. Nat. Mus.) thus proves of interest in determining that the creature was long-tailed, like Œstocephalus, Ptyonius, and Phlegethontia, but unlike the first two genera the neural and hæmal spines are not elongate nor marked with radiating lines. The neural spines are indistinct and if developed at all were very low and short.
The centra are short, cylindrical, and thick. They gradually decrease in size to where they are lost, since the portion preserved does not represent the entire length of the tail. There may have been 15 more vertebræ distally and 5 more proximally, thus making about 75 caudal vertebræ, as Woodward ([630]) has determined obtains in Ceraterpeton galvani Huxley.
The ribs are continuous throughout the length of the tail preserved and have precisely the same structure as is found in the dorsal region with the possible exception that the posterior alar expansion is not so well developed in the caudal ribs. The ribs are decidedly fan-shaped and articulate by a single head with a short transverse process. They are distinctly curved like all microsaurian ribs.
| Measurements of Specimen of Pleuroptyx clavatus Cope. (No. 4509, U. S. National Museum, Linton, Ohio, Coal Measures.) | |
| mm. | |
| Length of tail as preserved | 105 |
| Length of anterior vertebra | 1.5 |
| Diameter of anterior vertebra | 1 |
| Length of rib | 5 |
| Width of rib | 1 |
The above-described specimen represents what I suppose to be the posterior part of the body of Pleuroptyx clavatus Cope. The characters of the ribs and vertebræ are the same. The fragment is interesting, since it gives an insight into the form of the body, which was slender, conforming thus to other long-tailed microsaurs. Length of specimen, 65 mm.; width of specimen, 30 mm.
There is still a third example of this species among the collections belonging to the National Museum (No. 4484). The specimen includes a badly crushed posterior portion of a skull and a series of about 16 crushed vertebræ, with several pairs of ribs and ventral scutes.
Very little can be said of the skull save that the maxilla of the right side was long and bore from 15 to 20 teeth, of which 9 are preserved more or less completely. The mandible is likewise crushed and one can not determine its elements. Portions of 2 or 3 teeth are preserved. The form of the mandible is long and slender.
The ventral scutes are of the pectoral region. They are long, slender, and thread-like. They are not closely packed, but I count 12 in a distance of a millimeter.
So far as can be determined the vertebræ are the same as has been described for other specimens. They are short and heavy. The ribs show, for the most part, the same characters as the type specimen.