WEALDEN FORMATIONS. 15 



correspond in size and shape with those shown in situ in Theriosuchus, PI. IV. The 

 subjects of figures 4 — 1 I am disposed to refer to Nannosuchus. 



Crocodilian Scutes. PI. II, fig. 4, 5, 11, 12. 



In almost every slab containing Crocodilian remains are scutes, or portions or 

 impressions of scutes. They include the ' peg-and-groove ' type, the hexagonal with 

 sutural margins, and the ordinary quadrate with bevelled edges, either plain or single- 

 ridged. All show the Crocodilian pitted or reticular sculpturing on one side, the smooth 

 surface on the opposite. 



The scutes exemplified in Plate II, figs. 4 and 5, partly by portions, partly by 

 impressions, may be referred both by contiguity and proportional size to the larger 

 examples of Nannosuchus gracilidens. Some scutes of this type, of rather larger size, 

 and with the smooth, overlapped, anterior border relatively broader and more elevated 

 than in Goniopholis crassidens^ may belong to the smaller species of Goniopholis 

 {G. tenuidens) or to the larger kind of Brachydedes. A smaller-sized peg-and-groove 

 scute would fit Brachydedes minor ; the smallest and most numerous of all are 

 commonly associated with evidences of Theriosicchus jmsillus. 



The most instructive scutal fossils are those which exemplify the relative position 

 and mode of interlocking of the articular mechanism. Of these are figured two groups, 

 one showing the outer (ib., fig. 11), the other the inner (ib., fig. 12) surfaces. 



These specimens afford grounds for additions to the original description of the peg- 

 and-groove modification of Crocodilian armature. 



To the " process continued from one of the angles vertically to the long axis of the 

 scute "* may be added " from the anterior and external angle ;" and for " the depression 

 on the opposite angle of the adjoining scute " may be written " on the under surface of 

 the posterior and external angle of the scute in advance." 



When the medial dorsal series of scutes are seen in natural connection from the outer 

 surface the articulating peg is concealed, as in the two hinder pairs of the three shown 

 in fig. 11, PL 11. When the inner surface of a similar series is exposed, as in fig. 12, 

 the mode of application of the pegs and grooves comes into view. 



The scutes of the two medial rows along the back of these Purbeck Crocodiles join 

 each other at the medial line by a close contact of the inner borders — a kind of ' harmonia ' 

 or toothless suture. Ventral scutes usually show thicker, more sutural, margins. The 

 dorsal scutes upon the tail lose the peg and groove, are longest in longitudinal 

 diameter, and mostly support a longitudinal submedial ridge on the outer surface ; at 

 least in Theriosuchus imsillus (PI. IV, fig. 2). 



1 < 



2 c 



Supplement,' No. viii ; Pal. Vol., 1878, p. 2, PI. IV, fig. 1. 

 Report on British Fossil Reptiles,' 1841, p. 70. 



