THE MICROSAURIAN FAMILY NYRANIIDÆ, FROM THE COAL MEASURES OF OHIO.

Family NYRANIIDÆ Lydekker, 1890.

The type genus of this family was placed by Fritsch (251) with the ArchegosauridÆ, although its resemblance to Anthracosaurus was pointed out; it was subsequently made the type of a family by Lydekker (393) in 1890, and placed next the ArchegosauridÆ. Known from the Coal Measures of Bohemia, Ireland, and Ohio.

Two genera from North America, Ichthyerpeton and Cercariomorphis, are assigned tentatively to this family, both known from the Coal Measures (462) of Linton, Ohio, and both with the body completely scaled. The distinguishing characters are found chiefly in the shape and arrangement of the scales, the structure, form, and size of the body, all of which are given full treatment in the discussion below.

Genus ICHTHYERPETON Huxley, 1866.

The genus was founded by Huxley (334) for the reception of the species Ichthyerpeton bradleyÆ from the Kilkenny Coal Measures of Ireland. The remains of the type specimen represent "the hinder moiety of the trunk, with the greater part of the tail, of an animal whose scaly integument and laterally compressed, fin-like tail might easily lead one to take it for a fish, were not its true position among higher vertebrata settled at once by the digitate hind limb; while its alliance with the labyrinthodonts is indicated by the delicate spicular ossicles, which form a rudimentary dermal shield along the belly." (Huxley.)

Ichthyerpeton squamosum Moodie.

Type: Specimens Nos. 4476 and 4459, U. S. National Museum.

Locality and horizon: Linton, Ohio, Coal Measures.

The present species is based on well-preserved remains from the Linton, Ohio, beds. There are two specimens of the species preserved on blocks of coal and together they represent the greater part of the length of the animal. The species is located in the genus Ichthyerpeton, which was founded by Huxley (334, p. 351) on remains from the Coal Measures of Ireland, on account of the character of the dermal covering, which consists of small scales such as Huxley described in the form from Ireland. The specific characters of this form are the small size of the rounded scales, the attenuated tail, the apparent absence of limbs, the character of the ventral scutellation, and the slightly curved condition of the ribs.

It is estimated, from the portions preserved, that the animal attained a length of not less than 3 feet and its body was long and slender. It may have had an appearance similar to the modern caudate genus Siren, though there were doubtless 4 limbs present instead of 2. The slenderness of the body is at variance with the condition found in the type species Ichthyerpeton bradleyÆ Huxley, in which the trunk was rather stoutly built. The character of the anterior portion of the body in the present species can not be determined and the skull is wanting. There are no evidences of anterior limbs, although the ventral scutellation preserved would seem to include the pectoral region. No pectoral shields are preserved, nor are there any traces of pelvic girdle or limbs.

The preserved portions on one block include nearly the entire tail and the posterior region of the body, and on the other block the dorsal region of the body and the anterior portion of the tail, so that the two specimens supplement each other in an interesting manner. There are impressions of several vertebrÆ preserved. They are much the same in character as Huxley has described for the type species (I. bradleyÆ). They are short and thick and were probably amphicoelous. There are likewise preserved the remains of rather slender recurved ribs mingled in with the remains of the ventral scutellation and distinguished from the elements of the abdominal shield by their size and curvature. They are, apparently, single-headed, but the character of their articulation can not be determined. The ventral scutellation consists of fine continuous rods arranged in the regular chevron pattern. They do not seem to be divided into oat-shaped scutes, as is the case with the form described by Huxley. The ventral rods are closely packed for a distance of more than 6 inches, but as they are scattered their exact arrangement can not be determined. They seem to have extended to the cloacal region, but there are no evidences of the specialized clasping organs such as Fritsch (251) has described in the ventral scutellÆ of Ophiderpeton. The scales, which are well preserved on the tail, may have covered the entire body, since there are many scattered scales in the dorsal region of one of the specimens. They are slightly oval, tuberculate, and measure scarcely 1 mm. in their longest diameter. They show but slight evidences of having been imbricated, though it is likewise possible that they were simply inclosed within the integument, and somewhat separated from one another. The most posterior part of the tail preserved seems to indicate that the tip was attenuated. It was probably flattened from side to side. We may thus regard Ichthyerpeton squamosum as an elongate aquatic animal with a long, flattened tail, and since there were possibly no limbs or very small ones, it would be an animal highly adapted for life in the water. The present species is of interest because it represents an additional discovery of the scaled Amphibia in North America. The species previously known from the Linton, Ohio, deposits is Cercariomorphus parvisquamis Cope. Dermal scales have also been observed in specimens of Amphibamus grandiceps Cope and Micrerpeton caudatum Moodie (462, 478) from the Mazon Creek, Illinois, beds, and Sir William Dawson (208) described scales accompanying several forms from the Joggins deposits of western Nova Scotia.