STEliEOGENl'S CllOMERI. 
299 
of neural bones cannot be determined, but it seems certain that, as in tlie next species, 
the neural scries is separated both from the nuchal and pygal bones by the junction 
in the middle line of the anterior and posterior pairs of costals respectively. There 
are eight ])airs of costal bones, but the number of marginals cannot be made out. 
'I'he nuchal bone is large, but much narrower than in S. lib't/ca, so that, as 
Keinach has pointed out, it seems improbable that the anterior vertebral shield was 
narrower than the nuchal as in that species. Scarcely any trace of the epidermal 
shields is preserved, but the two middle vertebrals seem to have been large and 
roughly hexagonal in outline. 
Text-flg. 96. 
Carapace and plastron of Stereogemjs cromeri: A, carapace ; B, plastron, 
entoplastral bone; p'., gular shield; Hy.p., hyoplastral bone; Hyp.p., bypoplastral bone; inter- 
gular shield; Ms.p., mesoplastral bone; w., humeral shield; Nu., nuchal bone; p., pectoral shield; 
Xip., xiphiplastral bone, -f nat. size. 
(From the Ann. & Mag. Nat. Hist. [7J vol. xi.) 
The jjlastron (text-fig. 96, B) is relatively large : the bridge is long, being in the 
specimen described about 20'5 cm. in length ; while the length of the anterior free 
lobe is only 11-5 cm., and that of the posterior lobe about 15 cm. The anterior 
border is slightly concave in the middle line. The entoplastral [Ent.) is large and 
rhomboidal, the sides being somewhat convex. The sutures between the epiplastrals 
and hyoplastrals are concave in front and run forwards, terminating on the edge of 
2(i2 
