1910] Daniel: The Aiialiituij of Ilepleuielnis ntaeulal us 361 



have projecting from them ventrahvard haemal spines which serve as 

 a framework for the ventral lobe of the caudal tin. 



II. APPENDICULAR SKELETON 

 The part of the skeleton known as appendicular is a framework for 

 the fins and the girdles to which these, if paired, are attached. 



The Skeleton of the P.mred Fins .\nd their Girdles 



The Pectoral Fin.— The skeleton of the pectoral fin (pi. 29. fig. 4) 

 is fan-shaped, the proximal part of which consists of three basal 

 cartilages, pro-, meso-. and metapterygium ; from the last two of these 

 radiate numerous rows of radials. 



The propterygium (pr.p) is a small nodule located against the 

 mesopterygium. The mesopterygium ints.p.) is a stout cartilage, 

 from the enlarged distal end of which extend ten or twelve rows of 

 radials (m.) depending upon the amount of fusion which has taken 

 place proximally. The first or most anterior of these is made up of 

 large and irregular plates. The remaining rows are broken up into 

 small segments. The metapterygium (mi. p.) is a triangularly shaped 

 cartilage, the base of which points posteriorly. It is segmented both 

 proximally and distally and is then continued into the most distal 

 radial. Prom the metapterygium diverge numerous rows of preaxial 

 radials, in addition to which are several clearly marked posta.rial 

 radials (po.r.). 



The peetoral girdle in H< plauclnis is a slender arch unclosed 

 dorsally, to which the framework of the jiectoral fin is attached. It 

 is composed of a right and a left cartilaginous half which in 

 Heptanchus maeulatiis are united in the middle line below by means 

 of an unpaired median piece. The point of the girdle which extends 

 the more dorsalward is known as the scapular portion (sc). That 

 which by means of the median piece .joins a similar part from the 

 opposite side below is the coraeoid portion (eo.). At the middle and 

 postero-lateral part of each half of the girdle there is an irregular 

 surface for articulation with the pectoral fin ia.pf.). and in front 

 of and below this projection there is a broad surface for the attachment 

 of the ventral pectoral mu.scles. Perforating the girdles in this surface 

 is a large foramen (f.pf.) through which the blood and nerve .supplies 

 of the fin pass. 



Tlie Pelvic Fin. — The framework of the pelvic fin proper consists 

 of a longer posteriorly projecting ba.sal cartilage, the basipterygium 



