626 PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXV. 



of the group. It runs forward to the lower end of the clavicle and 

 attaches by simple suture, as the lower end of the hypocoracoid usually 

 does. Posteriorly it runs far backward. It appears as a process 

 from the hypocoracoid, there being no suture lietween them; ridges 

 and internal plates of bone are continuous between them. We can 

 but wonder why, if of dermal origin, it has not fused to the clavicle 

 as well as to the hypocoracoid, the former a bone supposed to be like 

 it, of dermal origin. 



In Aulostoinus there is a process extending })ackward from the hypo- 

 coracoid, which for most of its length is broken up into tine bristle- 

 like filaments. It does not appear at all externally. 



In Macrorhaiivphosm there are no interclavicles, unless the series of 

 bony plates along the median line of the breast and belly be consid- 

 ered as such. They can certainly not be considered homologous with 

 the parts so termed in GasteTosten.s and Fistulwrla. 



In the new genus ^Eoliscus Jordan and Starks, typified ))y Aviphhsi/e 

 strigata, there is no part homologous with the interclavicles of the 

 other forms, unless the posterior part of the hypocoracoid, which is 

 partly divided from the anterior part by the encroachment of the 

 lower actinost, be considered as such. 



The Shoulder Girdle of Gasterosteits i^ataphractus. 

 (1 asterosteid.e. 



The elements of the cranium are typical in number and arrangement 

 except the opisthotics are a'bsent. The parietals are widely separated 

 by the supraocciptal. On the superior surface the epiotic articulates 

 to the supraoccipital, the parietal, and the pterotic. On the posterior 

 subvertical surface it articulates to the pterotic, the exoccipittd, and 

 the supraoccipital. The pterotics form the outer lower angle of the 

 cranium. The articular facets of the exoccipitals are on a level with 

 the middle of the basioccipital. The concave '^ centrum" of the basi- 

 occipital is exceedingly deep. 



The post-temporal is a wide, nearly flat, ganoid bone, joined firmly 

 and broadly (but not by dentate or inflexible suture) to the epiotic 

 and pterotic. From its lower inner edge it sends a lower fork along 

 the under part of the pterotic to where that bone joins the exoccipital. 

 or to the place where the opisthotic typically is. 



The supraclavicle is represented by a very small scale-like bone 

 which is interposed between the clavicle and post-temporal, but not 

 suspending the clavicle lower than it would be were it attached directly 

 to the post-temporal. 



The upper end of the clavicle turns backward around the hypercora- 

 coid foramen. It shows exteriorly as a triangular ganoid plate behind 

 the post-temporal, bounding the upper part of the round, naked space 

 in front of the pectoral. The lower part of the clavicle runs obliquely 

 downward and forward. 



