211 



till the grooves bounding it disappear. The inferior lateral groove becomes 

 widened into a pit. which some of the specimens show to have been occupied 

 by a pluglike parapophysis, as in Elops, etc., or a rib-head of similar form. 

 The neurapophysial articular grooves become pits anteriorly, and these 

 only of all the grooves, remain on the anterior two vertebrae in the collection. 

 Some of the posterior caudals preserve large portions of the neural arches 

 and spines. They form an oblique zigzag suture with' the bodies, consisting 

 of two right angle's on each, one projecting upward anteriorly, another down- 

 ward behind. The neural spines are very wide and massive, and in close 

 contact antero-posteriorly ; these probably support the caudal fin. They are 

 deeply and elegantly grooved from the basis upward. The centra exhibit no 

 lateral grooves. 



An unsymmetrical ventral fin-ray accompanied these remains, and, from 

 its mineralization, color, size, and sculpture, probably belongs with them. The 

 anterior margin is thinned, and with obtuse denticulations; the posterior trun- 

 cate. The section is lenticular, with a deep rabbet on one side of the posterior 

 edge ; section at the base circular, apex lost. The sculpture consists of fine, 

 longitudinal, raised striae, which bifurcate and send numerous similar ridges 

 to the teeth of the anterior margin. This ray differs from the corresponding 

 one of I. anaides in its greater relative thickness, its anterior rugosity, and 

 peculiar sculpture. 



Measurements. 



M. 



Long diameter of tbe spine - 0. 0245 



Basal diameter pi tbe spine 0. 019 



Length of two eervicals (not distorted) 0. 033 



Diameter of the anterior 0.021 



Length of a dorsal 0. 016 



Length of a caudal 0. 014 



Width of the neural spine of the caudal at the base 0. 012 



Length of tbe alveolar margin of the premaxillary 0. 022 



Length of tbe anterior margin of the premaxillary 0. 020 



Depth from tbe condyle of the maxillary „ 0.026 



Length of the crown of the premaxillary tooth 0. 0042 



Diameter of tbe crown of the premaxillary tooth 0.002 



A fragment of a large flat bone exhibits very delicate radiating grooves, 

 which are marked by spaced impressed dots. 



From the North Fork of the Smoky River, Kansas, six miles south of 

 the town of Sheridan. Prof. B. F. Mudffe. 



This species was about two-thirds the size of the species last described. 



