Maryland Geological Survey 201 



tremities are rugose, indicating a heavy covering of cartilage. The 

 fibula is massive, and its distal end somewhat expanded. The astragalus 

 was free, and is wanting in the present specimen." 



The tibia (pi. xviii, fig. 3) has nearly the length of that of Morosaurus 

 grandis (No. 1905, Yale Museum) and but little more than half its 

 diameter, indicating an animal of much lighter build. Compared with the 

 type of Morosaurus lentus (No. 1910, Yale Museum) the tibia of Pleuro- 

 ccelus alius is at least half again as long. The dimensions of the type 

 are given in Marsh's description above, but there are no fore-limb bones 

 in the collection referable to this species so that the relative length of 

 fore and hind limbs cannot be ascertained. 



A metatarsal (No. 5687, U. S. National Museum) (pi. xix, fig. 1) may 

 be provisionally referred to this species, as it has about the same relative 

 proportions as that of P. nanus. It is surprisingly heavy when compared 

 with the tibia, however, having fully the bulk of the equivalent bone of 

 Morosaurus grandis. Its general form may be ascertained from the 

 figure. 



DIMENSIONS 



Length 185 mm. 



Breadth proximal end 142 mm. 



Breadth distal end 113 mm. 



There is a middle caudal (No. 5626, G. C.) (pi. xix, figs. 2, 3), which is 

 doubtless referable to this species. It is a solid bone, biconcave, with the 

 neural arch, which is missing, over the anterior portion, as in P. nanus. 

 Laterally, it has rather prominent keels, and two lesser ones on its ventral 

 aspect which terminate in the prominent chevron articulations. The 

 transverse processes were situated at the base of the neural pedicels at 

 about the mid-length of the bone. This bone, which is that of a fully 

 mature animal, is here figured. Its dimensions are : 



Length 105.0 mm. 



Width anterior face 132.0 mm. 



Width posterior face 128.0 mm. 



Depth of centrum 103.5 mm. 



Part of a large proximal caudal is also recognizable, but too defective 



to characterize. 



