G. R. Wieland — Upper Cretaceous Turtles, 121 



ginal-costal furrow crosses the posterior corner of Ml, inner 

 ends of M2 and 3, nearly or wholly coincides with inner bor- 

 ders of M4— 6 and crosses inner ends of M7-11 ; nuchal, large, 

 sub-pentagonal, anterior border nearly without nether or costi- 

 form process, straight as viewed vertically ; pygal marginal of 

 medium size, notched anteriorly : pleurals, 8 pairs, all uniting 

 by sutures with the marginals, with the distal ends as broad as, 

 or broader than, the proximal ends, and the flat ribs projecting 

 peg-like into pits in the marginals (gomphosis) : neurals 9, the 

 first 8 about twice as long as broad, — No. 1 with rounded ends, 

 Nos. 2-7 notched anteriorly, rounded posteriorly, No. 8, ellipti- 

 cal, No. 9 broader than long. Anterior pygal assymmetrical, — 

 large, uniting with inner border of 10th and 11th marginals ; 

 posterior pygal of sub-trapezoidal outline, broadest in front, 

 and with double curve in posterior border for reception of the 

 anteriorly notched pygal marginal. (The anterior and posterior 

 pygal are represented by a single pygal in Acloeus.) 



(2) Horn Shields. — The boundaries of all the horn shields 

 are delimited by uniform deep border grooving on the bony 

 plates: nuchal shield wide; 11 paired marginals, with a 



Figure k.—Osteopgis Gibbi type. Exterior view of plastron showing horn- 

 shield markings, x \. 



(1) Bone plates. — Ep, epiplastron; en, entoplastron ; hy, hyoplastron ; 

 hp, hypoplastron ; ocp, xiphiplastron ; /, /, foramina. 



(2) Horn shields. — H, humeral ; P, pectoral ; V, ventral ; F, femoral ; 

 I ? ?, region of indistinct inframarginals. 



