148 Scientific Intelligence. 



The crania which I have "are from 6 to 9 inches in length, and 4*3 to 

 6'6 inches in breadth ; the normal breadth being probably relatively less 

 than either of these measurements; all the crania having suffered a 

 greater or less amount of compression and expansion. A transverse sec- 

 tion of the central or posterior part of the cranium forms an arch from 

 l-J to 2 inches in height; the longitudinal profile exhibiting a depression 

 of the nasal extremity precisely the reverse of that shown in von Meyer's 

 figure, where the occipital plate is depressed by a distortion of the speci- 

 men. The length of the nasal plate is a little less than that of the oc- 

 cipital, and the angle formed at its posterior extremity is of 32°. The 

 borders of the cranial plates, with the exception of the nasal, exhibit no 

 absolutely straight lines, but all are more or less curved. 



(2.) Agasskhihys SuUivanti, N. Another species scarcely less com- 

 mon m the Cliff limestone of Ohio I have called by this name; portions 

 of the cranium having been obtained by Joseph Sulllvant, Esq., of Co- 

 lumbus, Ohio, from his quarries in the vicinity of that city, as early as 

 '1836, 



This species is larger than the last, the crania having a length of 10 

 to 12 inches or more, and fragments indicate a considerably greater size- 

 The relative breadth of the cranium was greater than in A. Manni, In 

 a fine specimen sent me by Dr. Mann, which has a length of 10 inches, 

 the greatest breadth is 8^ inches. The arch of the transverse section is 

 2 inches in height. The longitudinal profile forms a nearly uniform in- 

 clined plane from occiput to nose. The borders of the cranial scutcheons 

 are generally right lines, giving to the mosaic pattern formed by them a 

 more geometric appearance than in the last species. The nasal plate is 

 relatively much broader, and its posterior angle less acute (53°). 



A fortunate fracture of this specimen shows that the form of the cere- 

 bral cavity is as perfectly preserved as that of the cranial plates- Both 

 species are from Columbus, Milford and Sandusky, Ohio. 



The following are descriptions of the new genera Onychodus and Ma- 

 chseracanthus : — 



"OiVvcHOnus, Newb. Among the fossils sent me by Dr. Mann are 

 two specimens of what in his notes he very significantly calls a *'cla\v 

 jaw ;" of which I have seen a third and very beautiful specimen in the 

 hands of Prof. Hopkins, of Geneva, N. Y. 



This fossil consists of a series of remarkably acute and curved teeth, 

 closely set on a common base, all curving in the same direction, and ap- 

 parently erectile. The detached teeth are frequently found in the Cliff 

 limestone from 1 inch to 2 inches in length. They are much cur\^ed, 

 hkve a circular section towards the summit, are somewhat compressed 

 below, and expand at base into several prominent roots, of which the 

 most conspicuous are on the side towards which the point is curved. 

 Those teeth have a central cavity extending nearly to the summit: this 

 cavity is surrounded by dentine, simple in structure; and the whole is 

 covered by a layer of smooth and poUshcd enamel without striae or orna- 

 ment of any kind." 



"Mach^racanthus, Newb. Spines often of large size, flattened, 

 curved, ancipital, unsymmetrical ; dextral and sinistral edges and point 

 generally acute; base somewhat narrowed, losing the markings of the 



.A 



