16 PROF. G. H. HOWES ON THE SKELETON AND [Jail. 18, 



denies the existence of these, as has previously been stated ; but let 

 them be present or not, it is certain, should Giinther's observation 

 hold good, that they cannot indicate the original lines of separation 

 between pro-, meso-, and metapterygia, as now understood. 



IV. On the proximal Postaxial Elements of the Ceratodus Pelvic Fin. 



The cartilage which I have already described (figs. 1 and 3) as 

 directly connected with the postaxial border of the basal mesomere 

 of the Ceratodus pelvic fin is ray-like, but relatively powerful, in 

 one of the two specimens (fig. 1). In the other (fig. 3) it is alto- 

 gether smaller and segmented into but two pieces, instead of into 

 three, as in the former specimen. While it here meets the distal 

 end of the proximal mesomere, it is much more intimately con- 

 nected with the second piece of the axis than in the former speci- 

 men ; but on the supposition that the cartilage is homologous in 

 both fins, its condition in fig. 3 is precisely that which would result 

 from a further reduction of that of fig. 1, such as there is good 

 ground to believe, for reasons previously alleged, has actually gone 

 on. In the second specimen the cartilage in question is further 

 interesting, in that it bears one and is in close connexion with a 

 second of the proximal parameres. 



In the specimen figured by Giinther (14, pi. 36. fig. 4) already 

 referred to (p. 5), the proximal piece of the axis bears two carti- 

 lages. Fig. 4 is a reproduction of his drawing. The distal carti- 

 lage is ray-like, and stands related to the base of the proximal 

 mesomere as does an ordinary postaxial paramere to the corre- 

 sponding border of a typical mesomere. The proximal cartilage 

 appears to have been free of the basal piece altogether. It is, as 

 shown in the figure, plate-like, and I have little doubt but that it was 

 formed by the confluence of the basal ends of at least the two rays 

 whicb it carries. These skeletal elements, as they stand in Giinther's 

 specimen, combine the cliaracters of those of the two described by 

 me (figs. I & 3). The postaxial parameres are, as in my specimens, 

 much simpler than usual, and the whole series of lateral rays are in 

 his fin more uniformly distributed than in general. The basal 

 plate is (fig. 4, mt.), like the corresponding bar of fig, 1, in near 

 relationship with the proximal mesomere, although but loosely 

 connected therewith ; while it agrees with the corresponding element 

 of fig. 3 in giving attachment to a couple of rays. Comparing the 

 proximal postaxial elements of my two specimens and Giinther's 

 figure with the corresponding region of the pectoral fin-skeleton, and 

 reflecting that the typical metapterygium is formed by a confluence 

 of the basal ends of the rays of that region, I incline to the belief 

 that the vestiges in question represent that lobe of the fore limb 

 which I claim as the metapterygium, together with its associated 

 rays. 



Should the cartilages now under discussion have the morpholo- 

 gical value which I am seeking to establish for them as probable, 

 the well-known views of Gegenbaur (10, II), and Huxley (19) will 



