72 



THE EXTINCT BATRACHIA, REPTILIA 



u. 



Lin. 



6 



8. 



1 



8.5 



1 



7. 





8.5 





17.5 



Length, 



" to middle of deltoid crest, 

 Width of head, 



" shank at middle, 

 " condyles, 



A mass of induarted marl, with vivianite and oxide of iron from Monmouth County, N. J., submitted to mc by 

 Prof. G. II. Cook, contains the posterior part of the cranium of this species, with cervical, dorsal, lumbar and caudal 

 vertebrse, dermal plates and coracoids. The individual was immature, as shown by the non-anchylosis of the centrum 

 of the atlas, the neural arches, etc. 



The cervical has the small hypapophysis composed of two small separated tubercles slightly prominent. The 

 dorsal, with a prominent, hypapophysis which is trincate in front and at the end, has the round cup characteristic of 

 this species and the II. tenebrosus. The dermal plates are large, elongate-quadrate, considerably exceeding the 

 frontal region in width. Their fossae are in some deep, wider than the interspaces, in others smaller, the plate with 

 a broad smooth bevelled border. 



The cranium exhibits the specific and generic characters very well. The muzzle is broken off at the anterior 

 extremity of the pre-frontal bone, showing that there is no foramen as in Thoracosaurus. The acute posterior 

 extremities of the nasals remain. At the anterior border of the orbits the lachrymal is wider than the pro-frontal, 

 and the pre-frontal wider than the frontal. 



The pre-frontal suture does not extend further back than opposite the middle point of the diameter of the orbit, 

 No part of the orbital margins are everted, except for a. shorter distance on the malar bone. The temporal or crota- 

 phitc fossae are of about the same area as tin! orbits. The width separating them is very little less than one-half the 

 distance; between the orbits. The anterior wall of the foramen is not quite vertical as in II. tenebrosus, nor very 

 oblique as in another species. The sculpture is less marked than in the hitler, and though it would become perhaps 

 more profound with age, it is quite different in pattern from these. There are small pits near the orbital margins, 



and shallow grooves which incline backwards towards the median line, which is almost smooth. Then; are no grooves 

 or pits on the interparietal region. In II. obscurus there are large deep pits all over tin; frontal, which is concave, 

 and broad smooth margins and a median line of pits on the parietal hone. In the the third species (figured by Leidy 

 Cret. Kept., II., 8,) the pits are more numerous and the interparietal wider, and with marginal grooves. The ante- 

 rior face of the crotaphite fossa is very oblique, or thickened inwards below, while it is vertical in the II. 

 obscurus. 



II. brevispinis, 

 II. obscurus, 

 II. ?sp„ 



Poetfrontal Frontal .Parietal 



suture, width, width. width. 



.52 1.23 .0 



.8 2. .55 



.7 1.95 .08 



The surfaces of flu; malar, posffronfo-pai ietal and post-temporal arches are marked with distant shallow pits. 

 The superior concealed insertion surfaces of the supraoccipifa.l are largely exposed, and rugose. 



The basioccipital, sphenoid and pterygoids are more or less exposed. The first is vertical, with Iatcro-inferior 

 processes directed upwards. The sphenoid has a, very narrow exposure, but this is horizontal. The posterior-inner 

 processes of I he pterygoid lie closely appressed to the sphenoid anil basioccipital laterally. This arrangement is much 

 as in the living Cavialis gangeticus. The posterior nares are more anterior, however, and the septum not completed. 

 Their plane is perhaps a little above that of the orifice of the eustachian tubes. The lower extremity of the basi 

 occipital, has a, well-marked posterior keel. 



