MORPHOLOGICAL REVISION 



H5 



made out as a thin line in the matrix, which fills the back part of the skull; 

 its relations to the basisphenoid and quadrate are normal. 



The lower jaws lie in position between the upper jaws and the teeth 

 can not be seen. The articular region is low, and just anterior to this the 

 upper edge rises in a prominent coronoid process. The different bones of 

 the jaws can not be made out, but it is apparent that the dentary takes 

 part in the symphysis. 



The paratype confirms the points made out in the type. It shows 

 the pterygoids as broad plates, approaching each other in the middle line. 

 If there were any teeth on the pterygoids, they are too small to be seen 

 in the present condition of the specimens. Certain small openings, anterior 

 to the orbit in the type specimen, were considered as antorbital openings, 

 but, as these do not appear in the more perfect paratype, they are probably 

 accidental breaks. The type specimens of Cardiocephalus are not well 

 preserved and it was impossible to recognize the relationship of this genus 

 to Gymnartkrus from the description, but a direct comparison makes it very 

 apparent. Cardiocephalus has, in both specimens, grooves lying on the inner 

 side of the orbits, which seem to be natural and not the result of pressure; 

 also, the pineal foramen is extremely small or absent; because of these struc- 

 tures, which are absent in Gymnartkrus, the latter is retained in a separate 

 genus, although it is recognized that when more than the skull is known 

 the two may have to be united. 



Gymnarthrus was originally regarded as a reptile, but it may almost 

 as readily be placed among the Amphibia; because of its resemblance to 

 Cardiocephalus it is here placed provisionally in the latter class. 



Fig. SO- 



A. C. heteroclitu!. No. 4550a Am. 



Mus. X *. Upper view of 

 skull showing sutures. 



B. Same. Lateral view of skull 



shown in A. Lettering of 

 both figures as usual. 



C. Cricotus sp. No. 4551 Am. 



Mus. Much reduced. Lower 

 view of skull, showing elon- 

 gate Meckeiian opening. 



Genus CRICOTUS Cope (p. 72). {Plates 24,25.) 



Characteristic specimens: Nos. 4550, 4550.2, 4551, and 4552 Am. Mus. 

 Nat. Hist. Cope Coll. 



The best specimens of this genus preserved are Nos. 4550 and 4550a, 

 the type of C. crassidiscus. A large skull. No. 4551, shows little more than 

 the general form; the sculpture and sutures can not be made out. 



