378 PALEONTOLOGY OF OHIO. 



center is filled with tubercles also. There are few or no radii. The lat- 

 eral shields are narrow, and are tubercular medially, and radiate near 

 the margin. Abdominal rods bristle-like. 



Vertebra) short. The expanded neural spines commence over the 

 thoracic region, where thej^ are low ; they become well developed on the 

 posterior dorsal region. The caudal fan-shaped spines are large, the 

 neural and h«mal similar and undistinguishable. The dilated portions 

 form nearly equilateral triangles, which stand on moderately short pedi- 

 cels. They are weakly ridged, and each ridge is prolonged into a nar- 

 row acute tooth beyond the margin, of which eleven may be counted on 

 one of the best preserved spines. The longitudinal striae are terminated 

 near the pedicel by two others which cross obliquely from each side, and 

 meeting, present the appearance of the margin of a cup sculptured in 

 relief, from which the striae arise. Pedicels smooth. The spines are in 

 contact at their angles, thus forming a continuous line. In the typical 

 specimen there are six in a half inch, in another seven, and in a third 

 eight. A specimen originally described as belonging to this species, as 

 having ten in a half inch, may belong to the P. serrula. The ribs are 

 well developed and slender. 



No traces of fore limbs can be found in any of the numerous well-pre- 

 served specimens ; but in two of the specimens bones of the hind limbs 

 are preserved. In one of these the femur is a small bone, contracted at 

 the middle. Number of phalanges not preserved. 



Extent of spines in largest, .097 m. ; extent of spines in No. 2, .006; 

 extent of spines in smallest, .005; length of head in smallest, .018; 

 length from muzzle to femur of ditto, .0583 ; length of tail of ditto pre- 

 served, .037 ; length of femur ditto, .004. 



The abdominal rods are bristle-like, and the vertebrae do not display 

 any other processes than those described. 



The most abundant of the Linton Batrachians. 



Since the above was written several specimens display fully the atten- 

 uated muzzle of this species, with other characters. The mandible is 

 very deep posteriorly, and the postorbito-squamosal and quadrato-jugal 

 arches are evident. The orbit is large, the thoracic scuta small, and the 

 abdominal rods fine. 



Length of head, .016; length to orbit, .012; diameter of orbit, .004. 



The teeth are very acute, rather remote, and their bases are plainly 

 striate. 



