No. I.] THE GENUS OF FOSSIL FISHES. 45 



from below. These pelvic bones are, as stated by Professor 

 Cope, massive, and expanded vertically on the outer side to 

 support the facets for the ventral fin. 



The right and left bones are strongly sutured together. In 

 front of the facets and of the suture the bones become much 

 thinner, but wider. At the same time there is, descending from 

 the outer border of each bone, a crest of moderate height, 

 while from the same portion of the outer border there arises a 

 much higher crest, so that a cross-section of the pelvis in front 

 of the fin articulation would somewhat resemble this figure 



I ! j j. Just laterad of the inner border of each bone there 



is found on the upper side a prominent ridge, running from the 

 fin articulation toward the anterior end of the bone. On the 

 lower side, and nearly opposite the upper ridge, is a similar 

 ridge. Elsewhere the bone is very thin. If now the thin por- 

 tions of bone were broken and had crumbled away, there would 

 be left a thick process standing out on each side and two rods, 

 the ridges just described. Such was doubtless the condition of 

 the bones which Professor Cope figured. Just how far forward 

 the pelvic actinosts extended is not known, since those figured 

 by both Professor Cope and myself have been broken. In 

 Tarpon these bones are very long and slender. In Elops, a 

 close ally of Tarpon, they are relatively 

 shorter and also broader behind. 



Professor Cope has quite correctly de- 

 scribed the facets for articulation of the 

 ventral fin. My Fig. 1 1 represents the posi- 

 tions and forms of these facets. The bone 

 is that of the right side, and is looked at 

 laterally. The upper facet is for the recep- fig. n. — x.thaumas. side 

 tion of an articular surface on the base of vjew of articulation for pei- 

 the upper half of the first ventral ray ; the 

 largfe lower facet for an articular surface on the lower half of 

 the same ray. The other two facets are for succeeding rays, 

 or possibly for baseosts. There was undoubtedly a disc-like 

 baseost between the upper half of the first ray and the articular 

 surface of the pelvic bone ; and there may have been other 

 rudimentary baseosts. 



