ONTOGENY AND PHYLOGENY OF THE STERNUM 65 



derived from the ends of the coracoidal portions of the usually 

 single continuous pectoral girdle characteristic of sharks. Figure 

 11 shows the girdle of Notidanus from the ventral side with the 

 " intercepted cartilage .... temptingly like a presternal" 

 (Parker, '91). Figure 43, the first of the series of girdles shown 

 in plate 12, is another drawing from the same form. It would 

 seem that here is the initial material from which all later pre- 

 sterna might possibly be derived. 



The author is of course aware that neither Notidanus nor any 

 other living shark is the direct ancestor of the vertebrates, and 

 that the following phylogenetic series of figures does not neces- 

 sarily mean that the successively higher animals are direct 

 descendants of those immediately lower which are used for illus- 

 trating the points. 



Among the teleosts a complete girdle across the midventral 

 line is ordinarily lacking. However, several do have the clavicles 

 prolonged toward the center, and when so, there is quite uni- 

 formly a cartilaginous element in the midline which Parker 

 ('68) calls the 'epicoracoid.' 4 This lies between the coracoids, 

 in the identical position of a presternum. It is interesting to 

 note from figures 12, 13, 14, and 15, that this condition is so 

 closely alike in a ganoid, Polypterus (fig. 12) ; a teleost, Gobius 

 niger Linn. (fig. 13) ; and a dipnoan, Lepidosiren (figs. 14 and 

 15). A description of the condition in these three fishes may be 

 given in the account of Parker ('68) for that of Lepidosiren 

 annectens: "Lepidosiren agrees with the elasmobranchs in a 

 well developed epicoracoidal belt. Originally the epicoracoid 

 mass must have been double, and perhaps in a very early stage 

 each moiety was continuous with the coracoid proper, but a 

 wide transverse cleft was soon formed which separates epicoracoid 

 and coracoid." 



4 In this paper the term 'epicoracoid' is employed to designate the cartilag- 

 inous ventral ends of the posterior coracoids. The author is following here the 

 usage of Parker and others from whom many of the figures have been borrowed. 

 That this is not the correct term, he is well aware, and in another paper is sug- 

 gesting the term ' infracoracoid' as probably a more suitable one for these parts. 

 The term 'epicoracoid' was applied to the anterior element of the monotremes 

 bv Cuvier, and this use should be retained. 



