1S97.] XEW PALEOZOIC VEKTEBRATA. 75 



the type of the H. latus is smaller than the full-sized scales of the 

 European species thus far described. 



HOLOPTYCHIUS FLABELLATUS, Sp. ROV. PI. II, Fig. 3. 



Established on a nearly perfect scale from a green clay lamina 

 from the supposed Catskill of the '* Narrows " at Coxton, near 

 Pittston, Pa. The scale is in perfect preservation, the finest details 

 of the delicate sculpture being exactly preserved. 



In the coarseness and parallelism of the distal ridges the scale 

 represents those of the H. latus, rather than the H. leptopterus. 

 In form the scale is longer than deep, and oval in outline, while 

 that of the H. latus is as deep as long, and is rounded quadrate. 

 Whether this difference depends on the position of the scale is not 

 yet determinable. The border of the scale from one side of the 

 distal ridges to the other, is occupied by a broad band which is 

 marked by concentric grooves separated by wider convex inter- 

 spaces. From the proximal end of the coarse distal ridges radiates 

 a perfectly symmetrical fan of twenty-one ridges, each composed of 

 a series of small tubercles, which increase in size to the end of the 

 series. This fan measures half the long diameter of the scale 

 between the coarse ridges and the proximal border. The entire' 

 surface, except that occupied by the coarse ridges, is sculptured by 

 delicate line ridges and grooves of equal width, from the coarse 

 ridges to the circumference, as in the H. pUcatilis. The coarse 

 ridges are twelve in number, and two of them are bifurcate. They 

 are parallel in direction. 



Measurements. mji. 



Vertical diameter of scale 11 



Long diameter of scale 14 



Three distal coarse ridges 2 



Seven proximal concentric ridges 1.25 



Width of border of concentric ridges 3 



Eleven radiating ridges in i 



From the collection of Mr. R. D. Lacoe. 



Sagenodus occidentalis Newb. Rhizodus occide?italis Newberry. 

 Report of the Geological Survey of Illinois, Vol. ii, 1866, p. 

 19, Fig. 2. 



Three species of Sagenodus have been distinguished by scales 



