1880J NATURAL SCIENCES OF PinLADELPHIA. 239 



Fins scaleless, as is also a small patch on the anterior part of 

 the dorsal hump. 



Lateral line deflected near its origin, then running along the 

 median line of the bod^- to the origin of the caudal. Pores 

 simple. 



Color of the preserved specimen silv£r3--gray above, light 

 straw-color or creamy on the abdominal region and under side of 

 the head ; fins light uniform slat^-gra}'. The color is produced 

 by numerous dark dots upon the scales and membrane between 

 them, but fewer upon the scales, the outlines of which are there- 

 fore quite distinct. 



The hump is supported anteriorly by a very large trapezoidal 

 inter-neural, formed of a thick central pillar witli anterior and 

 posterior aloe, the latter twice as large as the former. The upper 

 margin of the bone is highest at the point of the central pillar, 

 from which it slopes anteriorly' and posteriorly. Tlie base of the 

 central pillar is broadly expanded transverseh', oftering a double 

 articulating surface on its under side. The next inter-neural is a 

 thin flat sub-rectangular plate, while the next three are expanded 

 above, attenuated below ; the fifth bent, and smaller than the 

 fourth, the loM'er portion of which is also bent forward. Inter- 

 neurals of dorsal fin with a central ray and an anterior and 

 posterior expansion dying out at their lower fourth ; symmetrical, 

 except that supporting the first two rays. Tliis is evidently 

 formed by two inter-neural bones, united by a thin bonj' plate, 

 which forms a broad expansion in front of the first, and a narrow 

 one behind the second. 



Upon the first vertebra there is a broad articulating surface, 

 apparentl}"^ for the reception of the first inter-neural, as a thin 

 longitudinal perpendicular partition exactly fits into a notch 

 between the two articulating surfaces of that bone. Tlie trans- 

 verse processes of this vertebra are broadly expanded inferiorly, 

 and their lower edges suturally united to a pair of ver}^ large bony 

 plates of complex form, connecting tlie air-bladder with the back 

 of the skull. 



From the anterior margin of each neurapophj-sis of the next 

 nine vertebne springs an upward-directed process, which, in the 

 first of these vertebnv, is almost as long as tlie neural spine, br,t 

 which diminishes in size on each successive vertebra. 



The neural spines of the first two of these vertebriie are bifid. 



