208 PROCEEDINGS OF THE ACADEMY OF 



Ptychodus polygyrus. 



Agassiz : Poissons Fossiles III, 156; Dixon: Geology of Sussex, 1850, 363. 

 Gibbes: Jour. Acad. Nat. Sci., 1849, 299, pi. 42, figs. 5, 6. 



Dr. Gibbes, in tlie work above noticed, figures two teetli, from the cretaceous 

 formation of Alabama, wliich he refers to Ptychodus polypfrm. Thej- clearly 

 bear a close lilieness to specimens of the European species of that name. 



A single specimen of a tooth, accompanying the Alabama specimens be- 

 longing to the Yale College collection, resembles the teeth of the European 

 Ptychodus polygyrus. The crown is nearly square or transversely oblong, with 

 the fore and back borders nearly straight, and the lateral borders convex. 

 The crushing surface is moderately convex and is crossed transverselj' by ten 

 coarse acute ridges, separated by similar intervals. The borders of the sur- 

 face, including the posterior sinus, are occupied by comparatively fine vermicu- 

 lar and interrupted ridges, appearing like granulations. The coarse ridges 

 are nearly straight, and at the end rather abruptly resolve themselves into the 

 finer vermicular ridges of the border. From European specimens of the teeth 

 of /'. polygyrus and P. lalissimus, this tooth appears especially to differ in the 

 proportionately greater degree of fineness of the bordering vermicular ridges 

 or granulations of the crown. Its measurements are as follows : 



Width of crown 13 lines; fore and aft 11 lines; height 5 J lines; width of 

 fang 8 lines ; fore and aft 6k lines ; thickness 3 lines. 



Of other species of Ptychodus, Agassiz mentions teeth of P. mammillarts, 

 found in the excavation of the Delaware canal, and preserved in the Museum 

 at Paris. (Pois. Fos. Ill, 151.) I have seen no specimens of that species 

 from an American locality. 



Synopsis of the Extinct BATRACHIA of North America. 

 BY EDWARD D. COPE, A.M. 



BATRACHIA. 



The vomer is double, and usually bears teeth in this class ; the premaxillary 

 is usually double ; Amphiumaand Spelerpes belli are exceptions. Teeth never 

 planted in deep alveoli. 



There are six orders, as follows : 



Trachystomata. 



Caudal vertebrre and frontal bones distinct. 

 Inferior pelvic elements not confluent. 



0. o. maxillaria, prefrontalia, palatina and pterygoidea wanting ; nasalia 

 present. 

 Ethmoid,* two lateral pieces, each forming part of palate. 

 Mandible toothless, condyloid. 

 No " postorbital and supertemporal bones." 

 First pair ceratohyals distinct. 



Proteida. 

 Caudal vertebrae and frorttal bones distinct. 

 Inferior pelvic elements not confluent. 



0. o. maxillaria, prefrontalla and nasalia wanting ; palatina and pterygoidea 

 present. 



Ethmoid,* a vertical plate on each side the cerebral lobes. 

 Mandible toothed, teeth pleurodont.f 



* Erroneously called orbitosphenoids by me, Jour. Acad. 1866 (on Anura). 



fThe statement made by Dr. Gray that the teeth of Neeturus are eanaled, as in venem- 

 ous serpents, V)y a channel entering at the base and issuing below the tip, appears to the 

 writer to be of doubtful accuracy. No other opening exists in the teeth of Neeturus m a- 



[Sept. 



