CHELONIA. 41 



carapace is well shown in this nodule, the marginal plates which join the nuchal plate 

 being preserved. The free extremity of the rib attached to the third costal plate 

 projects 1 inch 9 lines from that plate, and measures 7 lines in breadth, where it 

 becomes free ; the breadth of the plate being nearly 2 inches. The transverse curve 

 of the carapace is shown by this specimen to be much less than in the Chel. crassicostata. 



No. 4. Chel. planimentum. The nodule shows partly a cast of the outer surface of 

 the carapace, with part of the carapace itself. The outer angles of the third and 

 fourth vertebral scutes are here seen with the inner angle of the third costal 

 scute. The outer angles of the vertebral scutes are more prominent than in Chel. 

 declivis, Chel. subcristata, Chel. subcarinata, Chel. convewa, or Chel. longiceps ; they 

 resemble most those in Chel. breviceps. The breadth of the third costal scute is 4 

 inches. The characteristic angular ridge, formed by the narrow connate rib, where 

 it projects from the lower surface of the costal plate, is well shown in this specimen. 



No. 5. A nodule showing a cast of the under surface of the carapace seen from 

 above, apparently of the Chel. planimentum. 



No. 6. A nodule, 10 inches long f by 9 inches broad, showing a still more 

 imperfect cast of the under surface of the carapace, of apparently a younger specimen 

 of the Chel. planimentum. 



No. 7. A fragment of a nodule showing the outer dentated extremity of the left 

 hyosternal of the Chel. planimentum. 



No. 8. A portion of a nodule, with part of the carapace of the Chel. plani- 

 mentwm, showing the second to the seventh neural plates inclusive, and portions of the 

 second to the seventh costal plates of the right side, with more or less of their bony 

 substance broken away, exposing their coarse fibrous character, the fibres diverging 

 on each side from the subjacent rib, as they extend obliquely towards the periphery of 

 the carapace. The third neural plate is 2 inches 3 lines in length and 1 inch in 

 breadth ; it is crossed at its middle part by a moderately broad and deep channel, 

 indicating the junction of the second with the third vertebral scute. The third neural 

 plate is hexagonal ; the two shortest sides being formed by the truncation of the 

 contiguous angles of the second costal plates bending down a little to articulate with 

 them. The fourth neural plate is 2 inches 6 lines in length, and 1 inch 4 lines across 

 the broadest part. The anterior surface is concave, the posterior convex ; the two 

 longest sides converge towards the posterior surface, and are straight. The fifth and 

 sixth neural plates progressively decrease in length, without a proportionate decrease 

 in breadth. The breadth of the fourth costal plate is 2 inches 3 lines at its peripheral 

 extremity : its length is 6 inches ; the rib projects 2 inches beyond it. The upper 



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