448 CHARACTERS OF PALEOZOIC FISHES COPE. 



genus has a widely exijanded horizontal root, thus differing generically 

 from Styptobasis. 



The IStyptohafiis hniglitiana was found by Mr. Wilbur C. Knight (to 

 whom I dedicate the species with much pleasure), in what he determines 

 as the Permian formation in eastern Nebraska. It was a large shark 

 of carnivorous habits, and its presence indicates the existence of a marine 

 fauna whose remains have not yet been discovered. 



11. — On New Ichthyodorulites. 



Hybodiis regularis, sp. nov. Fig. 2. 



Dorsal spine elongate, gently curved to the apex from the middle. 

 Anterior border rounded, posterior rather broadly truncate, the latter 

 fissured to two-fifths the length of the spine froui the base, and two and 

 two-thirds times as far from the base as the commencement of the an- 

 terior sculpture. Tlie sculpture of the sides descends to opposite the 

 middle of the posterior fissure. Thus the naked inserted portion of the 

 spinels relatively short, and the sculptured portion is long. The latter 

 is also nearly plane. The sculptures consist of longitudinal ribs, which 

 are similar on the front and sides of the spine. Their interspaces or 

 grooves are as wide as the ridges on the front and the anterior half of 

 the spine, but they become narrower on the posterior half, while the 

 ridges are scarcely narrower. The latter are everywhere regular, and 

 do not inosculate, but run out successively toward the extremity on the 

 posterior side. Eight ridges may be counted on the side at the middle 

 of the length and thirteen near the base. Bottoms of the grooves 

 smooth. There is a wide smooth band of surface on each side of the 

 series of teeth, which is separated by an obtuse angle from the lateral 

 face. The teeth are small, acute, and directed downward. They form 

 two approximated rows, the teeth of one row alternating with those of 

 the other. ^ 



Measurements. 



Millimeters. 



Total length (10 millimeters added for apex) 'iUO 



Length of smooth base in front 48 



Length of posterior fissure 129 



Diameters at middle of tissure — 



Anteroposterior 2:5 



Transverse 14 



Diameter (anteroposterior) at middle of length 2'.\ 



Between apices of teeth of one row 10 



The fine specimen on which this species is based was obtained by 

 Jacob Boll from a soft Mesozoic limestone in Baylor County, Texas, 

 which is probably of Triassic age. The species approaches most nearly 

 the Hybodus major of Agassiz, from the Muschelkalk. In that species 

 the teeth are stated to be mere tubercles, which is not the case in this 

 species. 



