26 PROF. T. JEFFERY PARKER ON THE 



7. The Shoulder-girdle and Pectoral Fin. (Plate IV. fig. 6, and Plate V. fig. 18.) 



The only deviations of any importance from the ordinary Teleostean type in the 

 shoulder-girdle of Begalecus are the simple form of the posttemporal and its intimate 

 connection with the skull, and the abnormal position of the scapula, coracoid, and 

 brachials, correlated with that of the pectoral fin. 



The posttemporal (figs. 6, 8, 10, & 18, p.tm) is a small bone, flattened for the most 

 part, and closely applied to the dorsal surface of the auditory capsules, in a groove between 

 the epiotic and the pterotic ; its posterior end is thickened, and forms a saddle-shaped 

 articular surface for the supraclavicle. 



The supraclavicle (s.cl) is a gently curved bone, having on its dorsal (anterior) end 

 a saddle-shaped surface for the posttemporal ; its lower two thirds is flattened, and 

 applied splint-wise to the outer surface of the clavicle. 



The clavicle (cl) is a flat curved bone, having its dorsal half strongly bent forwards 

 and applied to the inner surface of the supraclavicle ; its lower half is sub vertical in 

 position. It is widest in the middle and narrows gradually to both ends. 



The postclavicle (p.cl) has the usual form of a long slender bone, attached by 

 ligament to the inner face of the clavicle and passing backwards and downwards; it is 

 about six inches long. 



The coracoid (cr) is rather a large bone, having a straight lower and curved upper 

 border ; it is attached by ligament to the posterior edge of the clavicle, and takes a 

 direction upwards and backwards. The outline is unbroken by the usual notch in the 

 posterior edge. 



The scapula (sc) is very small in proportion to the coracoid, an exaggeration of the 

 usual state of things in Teleosts, and especially in Acanthopterygians, and is an irregular 

 bone with a deep notch near the anterior end of its lower border. 



The pterygiophores or brachials (ir. 1-3) are three in number, and so closely applied 

 to one another as to appear like a single bone, the boundary lines between them only 

 appearing after drying. They lie in the same horizontal line as the scapula, being 

 tilted up posteriorly so as to bring the fin into its peculiar vertical position. The first 

 and second are roughly oblong, the third triangular, and all have about the same 

 vertical height as the scapula. Hence all four bones appear to form a single series, 

 and it is only by comparison with other fishes that the real homology of the scapula 

 becomes apparent. 



The pectoral fin (fig. 6, p.f) consists of thirteen unjointed rays ; but in front of the 

 first of them is a small nodule of bone, exactly resembling the proximal ends of the 

 other rays and evidently representing a rudimentary first or preaxial ray, thus bringing 

 the actual number to fourteen. 



The rudimentary ray and the first of the regular series articulate with the scapula, 

 a very usual connection, the second and third with the first or preaxial brachial, the 

 fourth to the seventh with the middle, and the eighth to the thirteenth with the 

 postaxial brachial. 



