PECTOUAL AND PKLVIC ARCHKS OK ARCIIyKUPTEUYX. 5 



Table of Measueements. 



ItiUM : mm. 



Greatest lengtli (as preserved) 39 



Length from middle of anterior acetabular border to 



anterior end 23 



Same measure to posterior end (as preserved) 16 



Width of acetabulum 6 



Greatest depth (at articulation for pubis) 15 



IscniDM: 



Greatest length 27 



Greatest breadth (at proximal end) 10 



Least breadth (near middle) 3 



Pubis : 



Greatest length 47 



Length of median sj'uiphysis of hinder expansion ]9 



Least breadth (near proximal end) 2 



Greatest breadth of hinder expansion 4 



The pelvis of Archceopteryx^ as now described, can be more 

 satisfactorily compared with that of the second specimen in 

 Berlin than the pectoral arch to which reference has already 

 been made. In the pelvic region, however, the Berlin specimen 

 is somewhat diflrerentlj crushed, all three elements being exposed 

 in direct side-view, with the femur in its natiual position ovei"- 

 lyiug them and obscuring the proximal end of the ischium. The 

 ligure published by Dames, 1897 (copied in PI. I. fig. 4), is, 

 indeed, ra.ther diagrammatic, and suggests imperfections in the 

 state of preservation of parts of the bones, which must be taken 

 into account. Small differences in shape between the ilium and 

 ischium of the two specimens have already been noted both by 

 Seeley (1881) and by Dames (1897), who include them among the 

 marks of at least specific distinction which they recognise in 

 the two skeletons. Still more striking differences now appear, at 

 first sight, between the pubes ; but it must be remembered that 

 in the British Museum specimen these bones are seen from 

 above, while in the Berlin specimen the right pubis alone is 

 exposed in outer side-view. Making allowance for the impei- 

 f ection of the proximal ends in the latter case, the relative length 

 of the ischium and pubis is approximately the same in the two 

 fossils, and the terminal expansion in the Berlin specimen may 

 well be the apparently cartilaginous mass (j;.) of the British 

 Museum specimen crushed fi'om side to side. Essential differ- 

 ences, therefore, are not yet demonstrated *. 



Among existing birds, the pubes meet in a symphysis only in 



* I am of opinion that future discoveries will result in demonstrating such 

 differences. I do not thinlf that a side-view of the pubes in the British Museum 

 specimen would correspond with that shovv-n in the Berlin specimen : I consider that 

 tlie cartilaginous end of the British Museum specimen is not homologous with the 

 bony expansion of the Berlin specimen ; and I conclude that there cannot have beea 

 any pubic symphysis in the latter. I therefore refer the so-called Archceopteri/M 

 siemenni to a distinct genus Arcliceornis, which will be defined by diflerentes in tlie 

 pectoral arch as well as in the pelvis. — B. P. 



