EXTINCT BATRACHIA. 379 



Ptyonius sereula, Cope. 



Proceedings Amer. Philos. Soc, 1871, p. 177. {Oestocephalus.) 



Represented especially by a single almost complete specimen, and per- 

 haps by another originally referred to the preceding animal. It is only 

 half as large as the P. pectinatus, but displays a more complex sculpture of 

 the pectoral shields, indicating that it is not immature. The tail is 

 relatively longer. 



The remains of the head indicate a trigonal outline, but the muzzle is 

 lost. The pectoral shields are narrow and elongate, both median and 

 lateral a little wider behind. The median has a considerable smooth 

 anterior prolongation. Its surface is near the middle sharply reticulate- 

 ridged, then closely radiate-ridged to the margin. The lateral shield is 

 reticulate-ridged behind, and sends out radii, those on the anterior part 

 subparallel. The triangular haemal spines begin far forward ; with the 

 neurals they are rather elongate deltoid i,n form, without the distinct pe- 

 duncle seen in P. pectinatus, but instead a short concave or crescent-shaped 

 base, from the concavity of which the sculpture rises. This consists of 

 ridges which extend beyond the intermediate spaces like teeth. Ab- 

 dominal rods hair-like. Ribs distinct. Remains of limbs not discern- 

 ible. 



In the second specimen alluded to weak limbs are seen on each side of 

 the posterior part of the abdominal cavity. On the right a moderately 

 stout femur is given off, which is followed by a broken tibia and fibula, 

 and then by five closely appressed metatarsals. The last are two 

 and one-half times as long as the space between them and the femur; 

 beyond them a few slender phalanges are moderately distinctly defined. 

 The tibia is more distinct on the left, but no tarsus nor phalanges ; 

 but some of the metatarsals remain. Length of limb to end of meta- 

 tarsals equal to five juxtaposed vertebrae, measured along the edges of 

 the neural spines. The limb, especially the foot, is slender. In this 

 specimen there are ten neural spines included in a length of half an 

 inch. 



In the typical specimen twelve neural spines are included in a half 

 inch. The dorsal vertebrae are somewhat dislocated in the anterior re- 

 gion ; nevertheless it appears that the length from the front of the pec- 

 toral shiel I is contained twice in the length of the tail ; in the smallest 

 example of P. pectinatus it enters the same .75 of a time, though perhaps 

 a very little should be added for the missing extremity. 



