Bliss.] 10 [June 15, 



support to a pair of very stout ribs. A long, and rather thick bone 

 extends from the extremity of each of these ribs to the posterior 

 point of the dermal plate of the third interneural spine. This bone, 

 which is serrated externally, forms one of the series of keeled der- 

 mal scutes which run along the side of the body. It is much larger 

 than the others, and its apparent office is to afford support to the 

 scutes. In Ox y dor as, the porous apophyses above described are 

 wanting, though the large ribs are present. 



In Doras- the hasniapophyses of the third vertebrae are not closed 

 beneath the centrum. 



The fourth anchylosed centrum is somewhat larger than the third, 

 and differs from it in exhibiting normal parapophyses with ribs of 

 the ordinary form. Its neural spine is united loosely to the neural in 

 front, and to the interneural of the second branched ray. As in the 

 third centrum, the hasmapophyses do not unite. 



In the Doradidas the different members of the coalesced vertebras, 

 and the interneural spines of the dorsal fin are so soldered together 

 and modified, that it is exceedingly difficult to distinguish them. A 

 comparison of Doras with Perinampus typus, however, will aid in 

 determining the relations of the neural and interneural spines in 

 Doras. For in Perinampus the interneural plates are so separated 

 from the bones of the cranium, and the spines themselves so slightly 

 united, that it is quite easy to trace them. But in Perinampus the 

 parapophyses of the coalesced vertebras differ widely from those of 

 Doras, for they are not separate as in this latter species, but unite to 

 form a broad, flat, scale-like bone, projecting laterally from the cen- 

 trums, and bearing, as Meckel has said, a striking resemblance to the 

 carapace of a chelonian. 



In connection with the structure of the dorsal fin in Doras, it will 

 be of advantage to make a comparison with the fin apparatus of the 

 first dorsal of Batistes, which, in some points of structure, resembles 

 that of Doras. 



In Batistes the apparatus which supports the first dorsal fin con- 

 sists of a number of bones, — the interneurals, — soldered together 

 into a boat-shaped piece which is attached anteriorly by ligaments to 

 the occiput, and supported posteriorly by a bony rod resting against 

 the fourth neural, and the first interneural spine of the second dor- 

 sal fin. This little boat has a deep keel, formed by the union of the 

 two sides. An oval, longitudinal opening in the sides of the boat in 

 its anterior part, affords exit for the two arms of the second spine of 



