Cope.] ^"^^ [Dec. 2, 



Al. 



Length posterior lobe from groin 0.155 



" median suture episternal 0.038 



" mesosternal 0.07 



AVidth " 0.095 



Thickness hyosternal behind medially 0.015 



" hyposternal " 0.020 



Width intei'gular scute 0.053 



Length gular (antero-posterior) 0.003 



' ' caudal sentum ...... 0. 083 



Width costal proximally No. 1 0.038 



" " " No. 2 0.055 



This fine species was discovered by my friend, J. C. Voorhees, in the 

 upper bed of cretaceous green sand, at Barnesboro, N. J. This gentle- 

 man is well known as the preserver of the unique and invaluable fossil of 

 the Lcelaps aquilunguis. 



ZYGOEAMMA. Cope. 



Genus novum familiae ? Adocidarum. 



Marginal bones of the carapace united wi h the costals by both suture 

 and gomphosis : the sutiare existing on the free marginals, as well as on 

 those of the bridge, the gomphosis inferior to and more distal than the 

 suture. Hyposternals uniting with the marginals only, by gomphosis. 

 Dermal scuta distinct. 



This genus is represented by a single species, which has left us but few 

 remains. These do not furnish positive indications for its reference to 

 the Cryptodire or Pleurodire divisions. The mode of union of the plastron 

 and carapace is, however, much more likely that of the Emydes and 

 Adoci ; and I therefore suspect it to be Cryptodire. 1'he character of its 

 sculpture is also that of the last named genus, rather than of Taphrosphys. 



Zygokamma stkiatula. Cope. 



Sp. nov. 



Represented. by five marginal bones, three incomplete costals, and both 

 hyposternals with their external margins broken off. These bones indi- 

 cate a species of light and elegant construction. The hyposteinals are 

 thin, and of nearly equal thickness transversely. Their sutures are very 

 coarse, and present but little irregularity at an intersection, in those of 

 opposite corners, excluding the other pair from contact, as is usual in 

 Adocus sp. The gomphosis of the hyposternal rises very obliquely. The 

 posterior lobe of the plastron has an acute margin, which continues as an 

 angle beyond the inguinal notch anteriorly. The fracture of the surface 

 prevents my ascertaining the existence of a series of intermarginal scuta. 

 The suture between the femoral and abdominal scuta divides the hypo- 

 sternals about equally. 



The marginals at and near the bridge are nearly twice as deep as long. 

 The posterior of the bridge is gently convex, with the margin a little 



