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line of the hack ; some of the latter having the character of shields. They 

 have the surface, in some species, marked with raised radiating ridges, or 

 inosculating ridges, whose edges are sometimes serrate. In a specimen 

 without a head, probably to be referred to the E. semianceps, the posterior 

 part of the side near the tail is covered with large, thin scales, with radiating 

 ridges on the exposed surface, which do not reach the edge. Some of them 

 bear the groove of the "lateral line;" but whether this was above or below 

 the vertebral axis cannot be ascertained. On the abdominal region of the 

 same specimen, there are three longitudinal rows of rhombic scuta : the two 

 inferior nearly in contact; the upper separated by a short interval. The 

 apices are directed forward, and the surface has a reticulate sculpture. 

 In another species, they appear to be smooth. 



The anterior part of the vomer is unknown I have, on a former occasion, 

 called the premaxillary bone the maxillary, and referred a premaxillary bone 

 of a species of Enchodus, found mingled with bones of the E. semianceps, to 

 this genus. The true premaxillary and maxillary being coossified in this 

 genus, I was long in discovering the real structure, which is described above. 



I formerly referred some of the species of Empo to the genus which 

 embraces the fish called by Leidy Cimolichthys levesiensis ; but I find that 

 they do not possess the same type of teeth. The Empo nepaolica belongs to it. 

 The generic characters originally assigned to the latter express the peculiari- 

 ties of dentition of the distal part of the premaxillary bone. The genus 

 therefore takes this name. From several allied genera here enumerated, it 

 differs in the presence of the -outer series of small teeth on the dentary bone, 

 and the inner series of the maxillary, with the absence of long teeth on the 

 front of the former. 



Empo nep.eolica, Cope. 



Represented by many specimens: the most perfect embracing a crushed 

 cranium, with body nearly to the posterior part of the abdominal cavity. 

 The cranial bones are light, and sculptured on the upper and external faces 

 with raised radiating ridges. There are large rhombic scuta on the dorsal 

 region and middle of the sides, which have radiating sculptured ridges; no 

 scuta below the line of the vertebrae are preserved on the specimen. Up to 

 the fourteenth-vertebra, the neural canal is not bounded by vertical laminae. 

 The neural spines are expanded on the "anterior base, as in many recent 



