250 



REPTILIA 



CLASS IIT 



ja-..'^^| 



Fig. 355. 



impressioiis of the membrane exhibit a number of longitudinal wrinkles or 



folds, and also numerous fine parallel Striae, 

 but are othervvise smooth. 



In the pelvic arch (Figs. 355, 356) the 

 ilium is low and extended antero-posteriorly 

 on either side of the imperforate acetabulum 

 as in Dinosaurs, the pre-acetabular portion 

 <X being much longer than the post-acetabular. 



N^"-^;:;^;^ Its anterior extremity is sometimes ex- 



panded (Bhamphorhi/nchus), in other cases 

 slender and tapering {Pterodadylus). The 



Pta-cMctvlus antiguns, Söm:n. sp. Upper ischium USUally fuses with the ililim, and 

 Jura ; Bavaria. Right lateral aspect of pelvis. excludes the Dubis from the acetabulum : 

 a, Acetabulum, belovv which is obturator . ^ ^ iii • i- 



foramen ; ii, Ilium ; is, ischium ; pw, Pubis. it is a much-expanded bone, pierced in most 



cases by a small Perforation. The pubis 

 appears to have been very loosely attached to the antero-inferior portion of 

 the ischium, and almost invariably occurs dis- 

 placed. Some authors regard this bone as a 

 pre- pubis, and Interpret the posterior ventral 

 Clement as a fused ischio-pubis. In Pterodadylus 

 the bone here called the pubis is much expanded 

 distally, and was probably united with its fellow 

 in a cartilaginous Symphysis. But in Bhampho- 

 rhi/nchus, Pteranodon, and Nydodadylus, it is 

 narrow and band-like, extending forwards for a 

 certain distance, and then beut inwards approxi- 

 mately at right angles so as to meet its fellow 

 of the opposite side, with which it becomes fused 

 in a ventral Symphysis. 



The femur is rather longer and more slender 

 than the humerus in some forms, but in others 

 is very much shorter, as in birds ; and as in birds 

 also, it is exceeded in length by the tibia, which 

 is stout and straight. The fibula is reduced to 

 a mere splint, often fused with the tibia, and its 

 pointed distal end extending scarcely half-way 

 down the shaft of the tibia, or it may be absent 

 altogether. There are two proximal tarsals 

 (astragalus and calcaneum), which in the Phampho- 

 rhyndiidae and Ornifhocheiridae are always fused 

 with the tibia. At least two distal tarsals are 

 always present. 



The bind foot is characteristically reptilian 

 in structure. The four inner metatarsals are 

 abtout equally developed, and bear clawed 

 phalan^es, havinsr the formula 2, 3, 4, 5, or some- „, ,. ^ ^ . . «„„„,. 



times, when the lirst two dlgltS are clawleSS, the Upper Jura; Eichstädt, Bavaria. Vi- 

 r 1 • 1 n ^ K rriu iiTi-i, J ' ' i. • 1 i. f, Femur ; ü, Ilium; is, Ischium; pf, 



lormula is 1, 2, 4, 5. Ihe nfth digit is almost pubis ; ^ Tibia. 



always shorter than the rest, its metatarsal 



reduced to a mere stump, sometimes without phalanges, and sometimes with 



Fig. 356. 



