DESCRIPTION OF PLATES, 13, 14. 647 



Fig. 6 a, Creusia spinulosa, shell, seen from above. 



6 b, 6 c, Creusia spinulosa, var. 1, scutum and terguni, internal 



"view of; 6 d, scutum and tergum, joined together, external 



view of. 

 6 e, 6f, 6 g, Creusia spinulosa, var. 2 ; 6 e, scutum, internal view ; 



6f, tergum, internal view of; 6g, tergum, of another 



specimen, internal view of. 

 6h, Creusia spinulosa, var. 3, scutum and tergum joined together, 



external view of. 



PLATE 14. 



Genera — Ceeusia, Chelonobia. 



Fig. 6 i, 6 k, 61, Creusia spinulosa, var. 4 ; 6 i, tergum, external view ; 

 6 k, the same, from another individual ; 6 /, the same, in- 

 ternal view of. 



6 m, Creusia spinulosa, var. 5 ; tergum, external view. 



6?i, 6o, 6p, 6q, Creusia spinulosa, var. 6 ; 6 n, scutum, external view 

 of; 6 o, tergum of same individual, external view of; 6p, 

 scutum of another individual, external view of; 6 q, tergum 

 of latter, external view of. 



6 r, Creusia spinulosa, var. 7 ; scutum, internal view of. 



6 s, Creusia spinulosa, var. 9 ; scutum and tergum, calcined to- 

 gether, external view. 



6 t, Creusia spinulosa, var. 10, scutum and tergum, calcined to- 

 gether, external view. 



6 U, Creusia spinulosa, var. 11, shell seen from above; 6u, 

 scutum and tergum, calcified together, external view. 



1 a, Chelonobia testudinaria, shell seen from above ; a specimen 

 has been chosen, with some of the radii smooth, and others 

 more or less notched ; 1 b, scutum, internal view of: 1 c, 

 tergum, internal view of; Id, scutum and tergum, joined 

 together, external view of. 



2, Chelonobia caretta, shell seen from above. 



3a, Chelonobia patula, shell seen from above; 3 b, tergum, ex- 

 ternal view of. 



4, Carina of Chelonobia patula, seen from within ; a a, outer 



lamina of wall, joined by the longitudinal septa to b, the 

 inner lamina ; e c e, sheath, descending to the base of 

 shell, with the middle -.part largely hollowed out ; the 

 upper part of the sheath, above d d, is transversely marked 

 by the lines of attachment of the opercular membrane ; 

 d, d, alse. 



5, View of the edge of the radius of the rostrum of Chelonobia 



testudinaria. 



a, a, inner portion of radius. 



b, thick outer lamina of the radius, transversely pitted ; be- 



neath this pitted portion, which forms only the outer 

 surface of the radius, and distinct from the inner portion 

 a, the arborescent and dentated sutural edges of this 

 outer lamina are ^een. 



