442 G. R. Wieland — Upper Cretaceous Turtles. 



Agomphus turgidus (Cotype). 



It is of interest to further note that the specimen (number 

 900) from the Cream Kidge Marl Co.'s pits Hornerstown, 

 Monmouth Co., New Jersey, received at the Yale Museum in 

 1869, is clearly a second specimen of A. turgidus Cope, from 

 the same locality as the type, and exhibiting various further 

 structural features. Indeed here is still another instance in 

 which more elements are present than in the above described 

 A. tardus, although without the fortunate distribution per- 

 mitting a restoration as in that specimen. These portions are : 

 the entoplastron and both hyoplastra (that of the left side 

 articulating with the nearly complete 3d marginal), the right 

 5th-llth marginals (the 6th and 7th having the superior and 

 inferior borders broken away), the pygal marginal and the 

 lower halves of the left 4th, 6th and 7th marginalia ; also the 

 second, a 6th or 7th neural, and the third and fourth neuralia 

 complete with the proximal ends of the left 3d-5th and the 

 right 4th pleuralia attached. 



The specific characters of A. turgidus have already been 

 commented on indirectly, so that further description of the 

 present specimen which has been of much use in determining 

 the preceding new species, is scarcely required. The original 

 fossil shell was doubtless complete, and had but a few more 

 fortunately situated elements been recovered a restoration 

 could be made. 



A. turgidus did not have as massive a shell as A. tardus, 

 but presents all the characteristic generic features distinguish- 

 ing Agomphus from Adocus / in particular the heavy shell, 

 the sharp to acuminate rather than rounded xiphiplastral end 

 of the plastron, and the marginalo-costal suture resting on the 

 marginals, instead of rising up onto the pleuralia beyond the 

 third marginal hornshield. 



Synopsis of the Characters of Agomphus. 



The description of the foregoing new species of Agomphus, 

 A. tardus and A. masculinus, and of the plastra of more or 

 less doubtful specific identity numbered 775 and 776 in the 

 Marsh collections, together with a topotype of A. turgidus, 

 finally acquaints us with the shell structure of this interesting 

 Upper Cretaceous genus as follows : 



Carapace. — Medium sized to small, of elliptical outline, 

 considerable depth, and with thicker walls in some species 

 than in any other known Testudinates. Composed of 49 bony 

 plates (one more or less, depending on the presence or absence 

 of 7th and 8th neurals), and without fontanelles. Hornshield 

 sulci small and line-like to indistinct. 



