Prof. H. G. Seeley on the Ornithosaurian Pelvis. 247 



Fisr. 7. 



which would lead me to doubt its being an articular facet. 

 In the Pterodactylia the prepubic bones are never anchylosed 

 together. On the other hand, the other pelvic bones are 

 commonly anchylosed together in genera from the Lias and 

 Oolites. In Pt. dubius there may be some ground for doubt 

 whether the pubis and ischium are not really one bone, as von 

 Meyer believed, because ossification appears to be incomplete, 

 and yet the two bones are blended, without trace of suture ; 

 but it is more probable that ossification has obliterated the 

 suture. It is these circumstances which led me to adopt the 

 view that the ventral part of such an ischio-pubis would have 

 a tendency to be limited to the ischiac region, because the 

 pubic part, freed from the usual mechanical stimulants to 

 ossification, would have a tendency to undergo atrophy and 

 shorten more and more, until the prepubis was brought into 

 contact with the prominence which alone remained to mark 

 the position of the pubis, as in Crocodiles. 



In the Khamphorhynchidse * the prepubic bones are much 

 more unsymmetrical, and commonly 

 have the form of a capital Y (figs. 7, 8), 

 in which one limb of the fork is reduced 

 in length or may be absent, though the 

 latter condition may be a generic 

 difference. In this family the pelvis 

 is relatively small ; the anterior pro- 

 cess of the ilium is relatively deep and 

 in marked contrast with the rod-like 

 anterior process of other family types. 



My own notes, written from the 

 specimens at Munich, are as fol- 

 lows : — 



" ' Bhamphorhynchus 3Iiinsteri } var. 

 longimanus ( Wagner). — The pre- 

 pubis is shaped something like a 

 boomerang and measures 1-gV inch 

 from end to end. It is angular in 

 front, with a projecting process in 

 about the middle of the lateral bor- 

 der." In other species this angular 

 process is absent, and the bones of 



the right and left sides are united together by median 

 symphysis into a bow-shaped bone without trace of median 

 suture. 



u Eh. Milnsteri (Goldf.). — The prepubic bones, attached to 



Rhamph. Gemmingi. 



Prepubic Bones. (Meyer, 



I. c. T. ix. fig. 1.) 



Fig. 8. 



Rhamph. Gemmingi ? 



Prepubic Bones. (Id. 



ibid. T. x. fig. 3.) 



* Ann. & Mag. Nat. Hist., August 1870. 



