TRIMERORHACHIS, A PERMIAN AMPHIBIAN 253 



(op. cit., p. 113), referred provisionally to Zatrachys. The cora- 

 coid has not been certainly recognized. The bone figured (Fig. 5, 

 E, F) is probably correctly identified; possibly it is the ischium. 

 There are no other evidences of pelvic bones, except of the ilia, 

 of which more than fifty are in the Chicago collections. I have 

 figured the relations of the quadrate in a specimen in which the 

 different elements had been separated (Fig. 3). The sutural 

 roughening for the pterygoid is very conspicuous. The separated 

 quadrate is not very rare in collections. 



Not a trace of any dermal ossicles has been detected in 

 any of the abundant material; the skin unquestionably was bare. 

 Certain skin ossifications or calcifications, however, have been 

 detected in a few specimens, first mentioned by Cope and later 

 by Case. They consist of very thin sheets, like leaves of thin 

 paper, probably of calcified cartilage, overlying each other, a dozen 

 or more, in places. They probably sheathed the under side of the 

 abdomen.^ 



The bones figured were all found dissociated, and probably 

 belong to different species, though there is not much difference 

 in size. A number of species of Trimerorhachis have been de- 

 scribed, though it is a futile and almost hopeless task to identify 

 them. I assume that the skull and pectoral girdle belong to 

 T. insignis, because they agree, so far as I can determine, with 

 the species so named. I cannot forbear entering a protest here 

 against the heedless naming of species of fossil reptiles, and espe- 

 cially of the Permian vertebrates, based upon fragmentary mate- 

 rial or, much worse, upon difference in size. Such names seldom 

 advance science. Nor does anyone care much, at the present time, 

 about species; they are, for the most part, a nuisance. Specific 

 determinations will become of use only when precise differences 



' Rather singularly dermal ossicles have very rarely been observed in the air- 

 breathing vertebrates of the American Permian — so far as I am aware only in Eryops, 

 though ventral ribs or scales are a rather common characteristic of the reptiles. Very 

 recently I have observed in Paniylus, the strange reptile of which only the skull has 

 been known hitherto, a continuous covering extending probablj'' over the whole body, 

 though possibly only on the under side, composed of a mosaic of small, smooth, bony 

 scutes two or three millimeters in diameter. The vertebrae and ribs show as great 

 peculiarities as does the skull. 



