1888.] ANATOMY OF THE MESOSUCHIA. 427 



rank as a rib ; and (2) of a much smaller component which, de- 

 scending from the neural arch upon the upper surface of the sacral 

 rib, thins out on this, and ends at a short distance from the base of 

 this. The long sacral ribs have a strong downward slant. Their 

 distal end is dilated, thus increasing the extent of the iliac articu- 

 lation. In a cross section through the middle of a sacral rib, the 

 vertical exceeds the horizontal diameter. The rib of the first sacral 

 vertebra is attached by a large base to the lateral surface of the 

 centrum close to its anterior end, but it does not contribute any 

 portion to the anterior, terminal, articular surface of the centrum. 

 The neurapophysis encroaches slightly on this surface. The anterior 

 terminal surface of the first and the posterior terminal surface of the 

 second sacral vertebra are distinctly concave. Their dimensions 

 exceed those of the applied surfaces of the vertebrae, which are nearly 

 plane, with a slight central depression. The rib of the second sacral 

 vertebra is attached to the side of the centrum nearly equidistantly 

 between the two ends, and no part of the costal suture approaches 

 either terminal surface of the centrum. The spinous processes are 

 tall, their antero-posterior extent is less than in the thoracic ver- 

 tebrae. 



Caudal Vertebra (Plate XVIII. fig. 5). — Their centrum is laterally 

 compressed. The lower border of the posterior terminal surface is 

 truncated by a double chevron facet. Their transverse process, 

 present in the front part of the tail, ossifies independently of the 

 centrum with which it is suturally connected, and thus is morpho- 

 logically a rib. 



Pectoral Girdle. 



The series of remains bearing the Cat. No. 30 comprises both 

 coracoids and the right humerus. Both scapulae are preserved 

 in series No. 31. Unfortunately no series contains both the coracoid 

 and the scapula. 



Scapula (fig. 1, p. 428). — Of the right only the ventral half is 

 preserved. The left comprises the whole bone, but both its ends are 

 defective. Together tbey give the form of the entire bone. This is 

 broader, shorter, stouter, and flatter than the scapula in extant 

 Crocodiles. The shaft is short and contracted. Above this narrow 

 part the antero-posterior dimension rapidly augments, chiefly by the 

 backward inclination of the posterior border. The outline of the dorsal 

 extremity is an arc of a large circle. The ventral end is deeply 

 indented by a notch which separates off a stout posterior part (ff c) 

 from a thin flattened process (jis), which in the articulated skeleton 

 appears to have been directed downwards and forwards. This 

 latter appears to correspond to the process termed acromial on the 

 anterior border of the scapula in some Anomodonts, and it suggests 

 the presence of a precoracoid element in these Mesosuchia, of which 

 the Eusuchia do not retain any trace. The stout process (ff c) is 

 subdivided into : — (ff) a posterior subcircular, smooth, hollowed 

 portion, obviously the scapular component of the glenoid fossa ; and 



