PECTORAL AND TELVIC ARCHES OF ARCJ3.EOPTERYX. 5 



Table of Measurements. 



Ilium : mm. 



Greatest length (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 



Ischium : 



Greatest length 27 



Greatest breadth (at proximal end) 10 



Least breadth (near middle) 3 



Pubis : 



Greatest length 47 



Length of median symphysis of hinder expansion 19 



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 differently crushed, all three elements being exposed 

 in direct side-view, with the femur in its natural position over- 

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

 figure published by Dames, 1897 (copied in PL I. fig. 4), is, 

 indeed, rather 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 hy 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 imper- 

 fection 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 (a\) of the British 

 Museum specimen crushed from side to side. Essential differ- 

 ences, therefore, are not } 7 et 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 think that a side-view of tbe pubes in the British Museum 

 specimen would correspond with that shown in the Berlin specimen : I consider that 

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

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

 any pubic symphysis in the latter. I therefore refer the so-called Areliceopteryx 

 siemensi to a distinct genus ArcJiceornis, which will be defined by differences in the 

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



