12 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



be rhomboidal in cross section. Downward projection short and 

 thin. Bar of moderate thickness nearly straight, the denticles 

 closely approximated without being in contact, long, slender, 10 or 11 

 in number, hardly half as long as the main cusp. 



At first glance this species seems identical with Eiiprlonwdina 

 coiiferta (see pi. 3, fig. 17) but the complete preparation of the speci- 

 mens established the entire absence of the denticles on the anterior 

 basal extension in P. curvidens. 



Occurrence. — Devonian (Rhinestreet) ; Shaleton, N. Y. 



C of y pes.— Cat. No. 11243, U.S.N.M. 



PRIONIODUS ARMATUS Hinde, 1879 



1879. Prioniodua armatus Hinde, Quart. Journ. Geol. Soc. London, voL 35, 

 p. 3G0, pi. 15, figs. 20, 21. 



We have no specimens corresponding to either of Hinde's figures 

 vzhich if properly drawn, represent two species quite distinct from 

 any herein described. For the present we must as.sume the figures 

 to be correct and the following four species w^hich are of the same 

 general type of structure are regarded as distinct. 



Occurrence. — Devonian (probably Rhinestreet) ; North Evans, 

 N. Y. 



PRIONIODUS UNDOSUS. new species 

 Plate 1, figs. 18-20 



This species belongs to the group in which the main cusp and the 

 lateral denticles incline more or less forward. This particular form 

 differs from the others in having the bar long, very slender, curved 

 (low^nwvard in the middle and its side with nodelike elevations at the 

 base of each of the lateral denticles. The terminal main cusp is 

 rather strong, nearly straight, longer but not greatly more so than 

 the first three or four denticles behind it. The denticles on the bar 

 are all very slightly curved and decrease rather regularly in length 

 posteriorly. The downward projection is strong and its anterior 

 side makes a straight line with the main cusp. 



Occurrence. — Devonian (Rhinestreet) : Shaleton, N. Y. 



Cotijpes.— Cut No. 11244, U.S.N.M. 



LIGONODINA, new genus 



General form of tooth as in PHoniodus but distinguished by 

 development of a series of suckerlike impressions on one side of the 

 downward extension of the main cusp. 



Genotype. — Ligonodina pectinata^ new species. 



Range. — Upper Devonian and Early Mississippian. 



