ART. 3 COXCEENING THE ARMOR OF TURTLES HAY 6 



above this rough surface is a patch of superficial bone 10 mm. high 

 and 5 mm. wide, and this is to be regarded as a part of the bone 

 which occupied the scar. On the rear of the ninth scute area is a 

 pitlike scar, 10 mm. long, which doubtless supported a nodule of bone. 

 On the tenth, eleventh, and twelfth scute areas the apices of the 

 toothlike projections of the marginal bones are rough and evidently 

 were beset with minute ossicles. 



On the right border of the carapace a rough sutural surface is seen 

 on the fourth scute area, while on the front of the fifth area is an 

 excavation which gives the impression that the bone of the fourth 

 area was nearly 30 mm. long and overlapped on the fifth area. On 

 the rear of the sixth area was a minute ossicle. A rough articular 

 surface on the rear of the seventh scute area indicates the former 

 presence of a boneiet 10 mm. long. A long splinter of bone, part of 

 which remains, ran along the whole lower border of the eighth scute 

 area, while on the rear of the ninth is a very distinct scale of bone 

 5 mm. in diameter. On the border of the tenth area is a rough artic- 

 ular surface, and a similar one is present on the eleventh. On the 

 twelfth area, near the midline, is a scale of bone 22 mm. long, loose, 

 and almost ready to drop out of its place. 



2. RESULT SECURED BY DR. H. VOLKBR 



In my paper of 1922 I endeavored to meet some of the arguments 

 advanced by Doctor Versluys against my views regarding the posi- 

 tion of Dermochelys. In so limiting myself I did not do justice to Dr. 

 Heinrich Volker, who, under the direction of Doctor Versluys, inves- 

 tigated in a thorough manner the skeleton of the trunk, of the limbs, 

 and of the skin. His results were published in 1913.^ On his page 

 516, Doctor Volker accepts the view that on the dorsal and ventral 

 sides of Dermochelys we must distinguish two layers of dermal bones, 

 a superficial (epithecal) and a more deeply placed layer (thecal). 

 To the epithecal, he concluded, belong the dorsal shield, or armor, 

 and the ossifications of the five longitudinal keels of the ventral side. 

 To the thecal layer belong the nuchal bone, perhaps vestiges of costal 

 plates retained on the ribs, and the bones of the plastron. The earli- 

 est recognition of these two wholly distinct layers of bone. Volker 

 says, is to be credited to the present writer. On his page 526 Volker 

 wrote "Mit Ha}'' und im Gegensatz zu Dollo (1901) nehme ich fiir 

 die gemeinsamen Vorfahren von Atheken und Thecophoren den 

 Besitz eines Doppelpanzers an." 



On only one important matter, as regards the structure of the 

 shell of the thecophorous turtles, does Doctor Volker differ from 



2 Spongers Zool. Jahrbiicher, Abt. Anat. Ontol., vol. 33, pp. 431-552, pis. 30-33 and 3 

 text-figs. 



