A DESCRIPTION OF THE GENUS DIMETRODON, COPE. 11 



cited. Another characteristic is said to be the presence of the intercentrum, a statement 

 agreeing with my own in the May number of this journal. 



" As the author of the paper does not think it necessary to allude to published sources 

 of information, it is too much to expect him to give credit for ideas communicated to him 

 verbally. All of the above mentioned and additional characters cited by Marsh in his 

 ' two opening paragraphs as belonging to the Permian Reptiles, Avith others, were explained 

 by me before the National Academy of Sciences, with Prof. Marsh as an attentive 

 listener, at its last meeting in Washington, April 18, more than two weeks before the 

 appearance of the paper here criticised. The characters to which I refer are ' the sepa- 

 rate premaxillaries, the immovable quadrate and the biconcave vertebras ;' the ' hypaxial 

 elements of the vertebras, called [by von Meyer] intercentral bones.' ' These intercentral 

 ossifications apparently exist in all the Reptilia yet found in this new fauna.' Compare 

 these statements with those found in my paper read before the National Academy (which 

 had been previously read before the American Philosophical Society, April 5) and pub- 

 lished May 8, and that Prof. Marsh profited by what he heard is evidenced by his use of 

 the term ' intercentra,' first introduced by myself. From this point of view it is easy to 

 understand his attempt to make it appear that Meyer first used the word. He says, 

 1 Another character of much interest is the presence of certain hypaxial elements of the 

 vertebrae, first observed by von Meyer in the Triassic genus Sphenosaurus, and called by him 

 intercentral bones (Zwischenwirbelbein)' (sic). ' As Ziuischenwirbelbein does not mean 

 intercentrum, but intervertebral bone, Prof. Marsh's knowledge of the former term must be 

 ascribed to some other source. The fact that the Amer. Journ. Sci. and Arts appeared 

 a good deal later than its usual date of publication may be considered in this connection." 



On May 8, 1878, 8 appeared the first more extensive paper of Cope on the forms from 

 the Permian of Texas. The following new genera and species were described : Diadectes 

 sideropelicus and D. latibuccatus ; Bolosaurus striatus and B. rapidens ; Pariotichus 

 brachyops ; Ectocynodon ordinatus ; Dimetrodon incisivus ; D. rectiformis and D. gigas ; 

 Epicordylus erythroliticus ; Metarmosaurus fossatus ; Empedoeles alatus ; Embolophorus 

 fritillus; Theropleura retroversa, T. uniformis and T. triangulata. A new species of 

 Clepsy drops, represented by numerous portions of the skeleton, was established — C. natalis. 

 The skull is described: "There is no quadratoj ugal arch, but the zygomatic and post- 

 orbital arches are present. The squamosal extremity of the zygomatic arch descends low 

 on the quadrate as in turtles, preventing mobility of the latter." " The symphysis of the 

 mandible is short, and the premaxillary bones appear to be distinct. The teeth were of 

 different sizes and the premaxillaries and canines are distinguished from the others by 

 their proportions. All are subround in section, with more or less defined anterior and 

 posterior cutting edges. The premaxillary teeth are larger anteriorly, diminish pos- 



