MORPHOLOGICAL REVISION 



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Genus ZATRACHYS Cope (page 47). 



Characteristic specimens: Nos. 4586, 4587, 4589 Am. Mus. Nat. Hist. 

 Cope Coll. 



The genus is known only from the skull, and but a single species, Z. 

 serratus, is identifiable. Cope, in 1884 (I, 18), remarked of this genus: 

 "Rugosities project in the form of teeth along the external alveolar border. 

 Individuals with sculptured neural spines and dermal bones are referred 

 here." This is right with regard to the serrated edges of the skull, but there 

 is no warrant for associating the forms having sculptured and expanded neural 

 spines, such as Z. apicalis Cope, with the skulls called Z. serratus and Z. 

 micro pthalmus; the expanded and sculptured spines are associated, in Aspi- 

 dosaurus, with a skull like Trimerorhachis. 



D E 



Fig. 43. 



A. Z. serratus. Lower view of posterior portion of skull, showing fine teeth on parasphenoid 



and pterygoid. No. 4589 Am. Mus. 



B. Same No. 4587 Am. Mus. Xi Diagram of skull, showing sutures. Lettering as usual. 



C. Zatrachys sp. No. 4584 Am. Mus. X K- Posterior view of humerus of left side. 



D. Zatrachys sp. No. 4560 Am. Mus. X K- Right scapula from outer side. 



E. Same from inner side. 



The type specimens were described by Cope without having been 

 cleaned; a little care has removed most of the matrix from two of the skulls 

 and it is possible to give a more accurate account of them. They are 

 longer than wide and very flat in the facial region; the orbital and post- 

 orbital portion is more elevated. The posterior edge of the skull and the 

 sides, as far forward as the nares, are ornamented by sharp, thin projections, 

 which are larger and more prominent posteriorly. Probably associated 

 with this specialization is the peculiar character of the sutures. The sur- 

 face of the bones has been largely destroyed, but enough remains to show 

 that there was a reticulate sculpture and a strong radial structure; the edges 

 of the bones are drawn out into fine points, closely interlocking with the 

 edges of neighboring bones and forming a very complicated suture. The 

 appearance is strikingly like that in many fishes. 



The region anterior to the orbits is very flat; two ridges run forward 

 from the orbits, separating this depressed area from a more elevated one 

 on either side. The orbits are on the elevated portion of the skull and sur- 



