282 ]\rr. II. G. Seelcy on Ornitliopsis. 



He compares' the fossil to the tympanic bone of Mosa^ 

 saurifs, -with ■which it certainly has no near resemblance. In 

 the Pala3ontogra})hical Society's vohuuc for 185-4 (Dinosaui-ia, 

 part 2), Professor Owen lii;urod a similar Lone, -which he 

 agreed with Dr. ]\Iantcll in regarding- as the tympanic bone of 

 Iguanodon (p. 18), but suggests that it may possibly belong 

 to Cetiosaurus or StrejHosjpondylus, This specimen I inter- 

 pret as the lower dorsal or lumbar vertebra of OrnitJwjysis. 



Dr. Mantell's description is as follows : — 



" In these bones the body bears some resemblance to a ver- 

 tebra, but the large cells or hollows Avhicli pervade it through- 

 out readily distinguish it ; it fonns a thick pillar or column, 

 which is contracted in the middle, and terminates at both ex- 

 tremities in an elliptical and nearly flat surface : two lateral 

 processes or alie jiass off obliquely, and are small in proportion 

 to the size of the column. . . . From the great size of the body 

 in the fossil and the extreme thinness of its walls, the tym- 

 panic ccllulffi must have been of considerable magnitude." 



In this description there is not one character which can 

 reasonably be presumed to characterize the quadi-ate bone of 

 IgxianodoHj or which is inconsistent with the identification of 

 the fossil as a lumbar vertebra ; for the cellular character, 

 which weighed with Dr. Mantell against making such a de- 

 tenu inatiou, is seen, from the previous description of a cervical 

 vertebra, to be evidence in its favour. The following charac- 

 ters are sho-wn in Professor Owen's or, rather, Mr. Dinkel's 

 figure. The centrum, from seven to eight inches long, shows 

 large internal air-cells and a dense outer film, like the speci- 

 men 28632. Posteriorly the articular surface is about four 

 inches deep, subcircular, and slightly hollowed. Anteriorly 

 the centrum seems to be larger; but tlie articular surface is not 

 presen-ed. The centiiim is subcylindrical, expanded towards 

 both ends, so as externally to be concave from front to back 

 all round. 



The pneumatic foramen is placed towards the anterior end 

 of the vertebra, between the centmm and the neural arch. It 

 is from two to three inches in length, compressed behind, 

 about an inch high, and rounded in front. 



The lunate mass, in Prof. Owen's figure, above the pneu- 

 matic foramen, is the transverse process. It is an exceedingly 

 thin and dense film, only comparable to the transverse process 

 in similar vertebraj of birds. 



The afhnitifs of this specimen arc in accordance with the 

 avian type. If supposed to belong to an animal of like species 

 with the cen'ical vertebra, it would resemble Pterodactyles in the 

 smaller size of the back relatively to the neck ; in the elonga- 



