BUFFALO SOCIETY OF NATURAL SCIENCES 



113 



portion are arranged into more or less longitudinal rows, while in the 

 posterior portion, where they are extremely numerous, they are 

 arranged into rough lamellae. Side walls covered with similar polished 

 rugosities and irregular punctag so characteristic that even the smallest 

 fragment of this species can be easily identified. Symphyseal region 

 prolonged downward in a short spiniferous process (this is not shown 

 in the type, but is seen in a paratype — E 2426). 



Remarks. — This species is represented in the collection by the type, 

 a specimen referred to above as the paratype, and a number of other 



Fig. 38. Ptydodus howlandi, n. sp. Left Lower Dental Plate in Outer (a), 

 AND Inner {h), Views. Type; Natural Size. E. 1919 



dental plates more or less perfectly preserved. The type and para- 

 type are practically perfect. They indicate a well-marked species 

 readily distinguished from all others. The special peculiarity of this 

 species lies in the fact that the tritoral region is divided by a depression 

 formed by the opposing upper tritor into two portions: an anterior 

 portion forming a sectorial edge just behind the beak and thickening 

 a little posteriorward; and a posterior portion — a tritor remarkable 

 for the fact that its outer face is a sharp edge, so that the dental 

 plate in this region was at once sectorial and trito'rial in function. 



