G2 Geological Society : — Prof. Owen on remai7is of 



difficulty, and lie therefore confines his remarks, in the present paper, 

 to indications of the characters by which it differs from previously 

 known extinct genera of Saurians. In the first place, Mr. Owen 

 shows, from the femur and other long bones having no medullary 

 cavities, but a eentral structure composed of coarse cancelli, that 

 the animal of which they formed part was of marine habits ; he, 

 however, adds, that the principal bone being a femur, independently 

 of the size and shape of the metatarsals, at once negatives the idea 

 that these remains belonged to the cetacean order ; and that the 

 form and proportions of the metatarsals equally forbid their reference 

 to any other mammalian genus. 



Femur. — The portions of this bone secured by Mr. Mackeeon in- 

 clude about the two distal thirds, excepting the articular extremity. 

 Its length is two feet four inches, its circumference in the middle or 

 smallest part of the shaft is fifteen inches six lines, and at the broken 

 distal end, two feet five inches. These dimensions prove that the 

 animal was equal to the most gigantic described Iguanodon*. If 

 the supposition of the proportion of the femur which has been pre- 

 served be right, this bone, Mr. Owen says, differs from that of the 

 Iguanodon, not only in the want of a medullary cavity, but also in 

 the absence of the comi:)ressed second trochanterian process w'hich 

 projects from the outer side of the middle of the shaft, and which 

 forms one of the several curious analogical relations between the 

 Iguanodon and Rhinoceros. The bone also expands more gradually 

 than in the femur of the Iguanodon, and the posterior part of the 

 condyles must have been wider apart in consequence of the posterior 

 inter- condyloid longitudinal excavation being longer and wider. Va- 

 rious other minor points of difference are noticed by the author. 



Tibia and Fibula. — The portion of a tibia which has been preserved 

 is compressed near its head, and the side next to the fibula is slightly 

 concave. The longest transverse diameter is eight inches nine lines, 

 and the two other transverse diameters at right angles to the pre- 

 ceding give respectively three inches three lines and two inches six 

 lines. The bone soon assumes a thicker form, its circumference at 

 about one-third from its proximal end being sixteen inches six lines. 

 The cancelli occupj-ing the central portion of the bone are arranged 

 in a succession of layers around a point nearest the narrower end 

 of the transverse section. Lower down the tibia again becomes 

 compressed, and towards the distal end the transverse section exhi- 

 bits a plate bent towards the fibula, and its narrowest transverse 

 diameter is two and a half inches. 



The portion of the fibula is eleven and a half inches long. In the 

 middle it is flat on one side, slightlj' concave on another, and convex 

 on the two remaining sides. It presents the same cancellous struc- 

 ture as the tibia, but the concentric arrangement of the layers of 

 cells is more exact. Towards the opposite end of the bone the con- 

 cave side becomes first flat and is then produced into a convex wall, 



* Femur of the Iguanodon, — length, 4 feet 6 inches ; smallest circum- 

 ference, 1 foot 10 inches. 



