454 JAMES ERNEST KINDRED 



The first branchial arch has elongated and is turned up laterally 

 to fuse with the pharyngobranchial cartilage which lies at the 

 laterodorsal margin of the oral cavity (figs. 13, 14). The pha- 

 ryngobranchial plate is also connected with the lateral end of 

 the second branchial arch, ending just posterior to it (fig. 14). 

 The third and fourth branchial arches have not as yet turned 

 up laterally, but they are longer than they are in the 8-inm. 

 stage. The fifth branchial arch has appeared as a pair of small 

 cartilages lateral to the procartilage continuum of the basi- 

 branchial plate of the fourth arch (fig. 14). 



SUMMARY AND CONCLUSIONS 



Under the classification of the teleosts by Gregory ('07), 

 Syngnathus is placed in the order Lophobranchii, which with 

 the order Hemibranchii (including Gasterosteus) , are grouped 

 into a superorder, the Thoracostraci. The important similarities 

 and differences of the chondrocrania of these two forms are 

 stated in the following summary. 



Both Gasterosteus and Syngnathus are alike in the following 

 chondrocranial characters: the presence of an elongate ethmoid 

 region; the acrartete articulation of the palatine cartilages; the 

 incomplete cranial roof; the horizontal position of the trabeculae 

 cranii and the parachordal cartilages; the presence of two septa 

 semicircularia in each otic capsule; a prootic process separating 

 the trigeminal and facialis nerves from each other; an elongate 

 fenestra basicranii posterius; a common foramen for the glosso- 

 pharyngeal and vagus nerves between the otic capsule and the 

 occipital arch; a small pterygoquadrate cartilage; a large inter- 

 cranial notochord; a postorbital process at the anterior margin 

 of each otic capsule. 



The above characters wherein Syngnathus resembles Gastero- 

 steus indicate the direction in which the skulls of these two forms 

 have become specialized. In addition, further specializations 

 are to be noted in the chondrocranium of Syngnathus : 



1. The modification of the anterior end of the ethmoid plate 

 by turning dorsally in the 8-mm. stage. 



