EDENTATA OF THE SANTA CRUZ BEDS. 14! 



ing to a definite plan. The posterior and larger part of the shield is 

 formed by two transverse bands of four plates each, with the median pair 

 of each composing a group of four large plates, the largest of the entire 

 structure ; next in front is a transverse band of five plates, three of moder- 

 ate size and on each side of this group a very small marginal plate. The 

 anterior portion of the shield, which is considerably narrower and contracts 

 forward, is made up of at least nine plates ; there is a central scute, elon- 

 gate, narrow and coffin-shaped, a difference from Propalceohoplophorus, in 

 which there are two such plates, but each is asymmetrical by itself; on 

 each side of this central scute is a longitudinal row of three much smaller 

 scutes, while two small ones complete the shield in front. In addition to 

 the twenty-two plates described, is a line of four very small plates over 

 each orbit, the smallest of the cephalic scutes. 



The ornamentation of the cephalic plates resembles that of the preced- 

 ing genus with characteristic modifications. On the median posterior 

 pair the grooves are shallow and the pattern is obscure, but there are two 

 concentric rings of conspicuous piliferous pits ; the other scutes, especially 

 those of the anterior region, have much deeper grooves and the included 

 figures are in correspondingly strong relief, which is far more marked 

 than in the preceding genus, while the surface of the plates is much 

 rougher and more coarsely punctate ; the small supraorbital scutes have 

 no definite pattern, merely a pitted surface. 



As a whole, the cephalic shield extends from the occipital crest to some 

 distance in front of the orbit, leaving the greater part of the rostrum ex- 

 posed ; laterally it roofs the temporal fossae and the orbits, reducing the 

 opening of the latter to a curiously small size. 



In form and construction the carapace (Plates XIX, XX) resembles 

 that of the preceding genus, and we find at least two movable bands on 

 each side in the anterior region, each band being composed of seven 

 plates. Behind these bands are seventeen transverse rows of plates, 

 which are smaller and thicker near the lateral borders, becoming larger 

 and thinner dorsally; they also increase in size posteriorly to the 

 pelvic region, whence they again diminish toward the posterior border. 

 The median dorsal area is thus a broad band of larger and thinner 

 plates, which attain their greatest size in the pelvic region. The lateral 

 margins of the carapace are slightly serrate and the posterior border 

 strongly so. 



