G. R. Wielancl — Upper Cretaceous Turtles. 435 



(2) A. petrosus Cope, (3) A. turgidus Cope, (4) A. (Amphiemys) 

 oxy sternum Cope, and (5) Aclocus {Pleurostermini) pectoralis 

 Cope, — all of which are either slightly or not illustrated and 

 difficultly accessible or little known types, based on fragmen- 

 tary materials of barely diagnostic value beyond family or 

 generic limits. It appears, however, that in comparison 

 with Agomplius tardus (sp. nov.), A. (Emys) firmus was a 

 larger form with a shell relatively but not nearly so extremely 

 heavy ; that A. turgidus Cope (as further described from the 

 Marsh Cotype JS~o. 900), is a small turtle of about the same 

 size as A. tardus with minor differences of form and horn- 



Figuee 6. — Agomplius tardus (type). x %. Outlines of the anterior 

 sutural faces or transverse sections of the 1st, 2d, 8th, 10th, 11th and pygal 

 marginals. — C, pit in anterior face of the right 1st marginal for the recep- 

 tion of the costiform process of the nuchal, which entirely perforates this 

 marginal ; S, sutural face for union of 8th marginal with the hypoplastron. 



shield boundaries and far less robust plastron ; that A. petrosus 

 Cope had a steeper, less flanged or shovel-shaped nuchal region, 

 with the hornshield sulci nearer the marginal border, and the 

 plastron lighter; that Adocus (Pleitrosternum) pectoralis had 

 a much less massive plastron and narrower bridge than A. 

 tardus / and that finally A. {Amphiemys) oxy sternum from 

 the Tertiary of Georgia is a fairly distinct species from all of 

 the foregoing Cretaceous Agomphids. 



