628 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



The Shoulder Girdle of Aulorhynchus flavidus. 

 aulorhynchid.e. 



The posterior elements of the cranium resemble Gasterostem in bein^ 

 more t3"pical in arrangement than in other examples of the order. 

 The pterotics form the outer lower angle of the cranium, and the 

 articulations of the epiotics are the same. 



There is but a single plate joining the clavicle to the cranium. It 

 is one of the series of lateral line plates, bearing a tube continuous 

 with the lateral line sensor}^ system, and it is in no way differentiated 

 from the rest of them. It is attached to the cranium over the pterotic 



Fig. 2.— Left shoulder girdle of Aulorhynchus flavidus from outer side, a, actinosts; d, 

 clavicle; hyoc, hypocoracoid; hupc, hypercoracoid; Up, lateral line plates; p, postclavi- 

 CLE, and pt, posttemporal. 



and the epiotic. Over its anterior end is a small bone bearing a 

 branched tube of the sensory system, which directs one branch ak)ng 

 the pterotic and another over the occipital region. It is typical in 

 shape and function of the supratemporal. 



The upper part of the clavicle turns l)ackward in a triangular proc- 

 ess as in Gasterosteus. The lateral line system of bones is attached 

 along its upper edge and is continued backward along the side of the 

 hodij. The lower part of the clavicle is slender and is inclined 

 obliquely downward and forward. 



The hypercoracoid foramen is boimded for a very short space along 

 its anterior side bv the clavicle. 



