VERTEBRATES. 3H 



puncta? being encircled by a slight rim or raised border — a not unusual 

 feature in the surface structure of teeth of widely distinct families of 

 Carboniferous Selachians. The base is thick, massive, nearly as exten- 

 sive laterally as the coronal region, in depth somewhat exceeding the 

 hight of the crown, from which it projects backward at a slight angle 

 to the vertical plane, posterior face gently arched, posterolateral angles 

 sharply rounded, anterior face moderately excavated, inferior surface 

 smooth, beveled at a slight angle to the horizontal plane, posterior mar- 

 gin obtuse, anterior and posterior faces roughened by vertically disposed 

 vermiculose markings. Viewed from above the crown presents a gently 

 arched outline, the extremities directed forward, the transverse diame- 

 ter equaliug, if not exceeding the elevation of the same parts. Great- 

 est length of tooth .87 inch, hight .3S,-antero-posterior diameter across 

 the median cone .30, greatest elevation of crown .17 inch. 



The present form is described from a specimen obtained from the 

 upper portion of the Lower Coal Measures of Iowa, by Mr. J. A. Allen, 

 to whom we have dedicated the species as a slight token of esteem. 

 INot absolutely entire, it preserves the median cone and one of the lat- 

 eral wings and base in a nearly perfect condition, enabling its distinctive 

 characters to be tolerably clearly defined, as also a satisfactory compari- 

 son with other forms. Of the Coal Measure Orodi, the above species 

 bears closest resemblance to 0. (?) corrugatus. Is. and W. ; it differs, 

 however, from that form in the more prominent median cone, and fewer 

 and proportionately stronger coronal corrugations. Its closest ally is 

 found in a species from the Upper Burlington limestone, 0. variocostatus, 

 from which it is distinguishable by its more symmetrical form, relatively 

 deeper and more massive base, and more regular corrugation of coronal 

 surfaces. In consideration of its geological position, it deserves close 

 comparison with the forms of Agassizodus from the same deposits ; but 

 its apparently equally strongly vertically plicated anterior and poste- 

 rior coronal surfaces would seem to preclude its reference to that genus, 

 while they suggest intimate relationship with typical Orodus. 



Position and locality : Upper part of the Lower Coal Measures ; 

 Creene county, Iowa. 



Genus AGASSIZODUS, St. J. and W. 



Zophodus, Dewberry and Worthex, 1870, 111. Eep., Vol. IT, p. 360 ; not Lophodus, Romaxowskt, 1864., 



Lare in the autumn of 1873, one of the writers was favored with a 

 communication from Prof. B. F. Mtjdge, Director of the Geological 

 Survey of Kansas, in reference to the discovery of the remains of a 



* Disc, de qneques reatea de Poiasona Foaailea, trouyes daDa le calcaire carbonifere da G-oaverne- 

 ment de Toala. Par Hennadina Romanowsky ; Moscow, 1864. 



