192 



THE EXTINCT BATRACIIIA, REPTILIA 



tag of a sharp unserrated or simple cutting edge. These aonte edges or oarinse separate faces, of which the posterior 

 is more convex. The crowns of these teeth were measured by Dr. Fisher, as follows: 



Inch/;*. Inches. 



First, anterior Hire, 1 4-8 posterior, 1. 7-8 



Second, " " I 8-8 " 2 



Third, '• " 12-8 " 22.8 



The pulp cavity extends about as far into the root as the crown, excepting its entrant foramen in the former. 



The mode of succession of the teeth is well seen in this specimen, and illustrates the process as indicated by Leidy 

 (Cretae. Kept., p. 51). The fang-like basis of the functional tooth undergoes extensive excavation by absorption to 

 furnish space for its successor, the remaining portion in some places being reduced almost to a shell, yet remaining 

 firmly adherent to the alveolar walls, without the slightest evidence of displacement. This and other specimens ex- 

 amined, prove that the old tooth is not removed till the process of absorption has extended to the alveolar margin, 

 when the crown is easily detached. 



The splenial bones present the usual remarkable character. At the posterior extremity of each, the articulating 

 cavity is narrow ovoid in form, subacuminate below, and not so broadly rounded as in the M. dekayi (fig. 47). 



Inches. 

 P. 0,K 



1.75 

 4.5 



2.25 



Long diameter, 



Transverse, 



Total depth of splenial at extremity, 



Of rounded face below dentary plate, 

 The surface appears to be adapted for motion in two directions. 

 The vertebra which accompanied the jaw measures as follows: 



Length centrum, 4.7 



Width anterior articular face, 4-55 



Depth " " " 4 - <i5 



Tt is a, dorsal with diapophyses below the middle; between it and the neural arch, near the articular extremities, 

 the surface is marked with sub-longitudinal ruga'. 



This Mosa.sa.ur could not have been less than eighty feet in length. * 



As compared with M. giganteus, this species presents considerable affinity. The Maastricht animal was some- 

 what smaller than either of those here described, the length of the quadrate bone being in. 4 lin., or move as ill our 



specimens of M. dekayi. Its elevated sub-pentagonal lumbars and caudals are also more as in M. dekayi. The non- 

 coalescence of the anterior chevron bones in M. giganteus, may be owing to Immaturity. As compared with that of 

 M. maximus, the os quadratum presents several differences and resembles Unit o("M. dekayi. Thus the articular ex- 

 tremity which extends over the ala is small, as in that species; the median posterior ridge is rudinicntal in the same, 



not a strong process as in M. ma.xinius, and the knob is small, the posterior decurved process of the proximal articular 

 face nearly in contact with it. The distal longitudinal rib is relatively twice as long in M. giganteus as in M. maxi- 

 mus, and more as in M. dekayi. other peculiarities arc easily found, which may l>c of little Importance. The exter- 

 nal part of the distal articular face is pinched up; not at all in M. maxhnus; the lower part of the ala, is much more 

 incurved and the groove on its margin much deeper. 



The M. dekayi may attain the dimensions of this species, though none such have come under my observation. 



From the lower marl bed of the upper cretaceous, from Monmouth Co., N. Jersey, 

 and Lumberton, Gloucester Co., N. Jersey. 



M08ABAURU8 PEINOEPS, Marsh. 



Sillim. Amcr. .iouin. Sci. Arts, IS!!!), p. 898. 



Prof. Marsh describes an individual of almost equal size to the preceding, which he distinguishes from them by the 

 form of the quadrate bone, lie says that the knob near the meatus is well developed; and the proximal articular ex- 



» i must express mj Igatlons to Dr. Fisher, tor the opportunity of examining the above specimens, as well as for the use of his notes, from vrhloh «nv- 



eral extracts are made in the above description. 



