II GENUS SEBASTODES. 579 



skulls. The following West Coast species were not avail- 

 able : ciliatus, proriger, brevispinis, umbrosus, nigrocinc- 

 tus, alutus, serranoides, nif'us. melanostomus, rupesiris, 

 cos, cercus, gilli, zacentrus, sinensis. 



The series upon which the following conclusions are 

 based consisted of fifty-one skulls of thirty-two different 

 species. Although many skulls could not be procured, 

 the series is essentially complete, containing representa- 

 tives from all parts of the group. 



The cranial characters that have hitherto proved useful 

 relate to the cranial ridges and the spines in which they 

 end. The characteristic spines and ridges are: the pre- 

 ocular on the anterior superior border of the orbit; the 

 supraocular, near the edge of the frontal bone above the 

 middle of the orbit; the postocular, behind the supraocu- 

 lar, and the tympanic, behind the postocular on the frontal 

 bone near the superior posterior angle of the orbit; and 

 the parietal, present in all the species, a longitudinal ridge 

 on the middle of the parietal bone. Of these ridges all 

 may be absent except the parietal,* and in the different 

 species in which they are present differ exceedingly in 

 the degree of their development. 



In a comparison of the crania some characters which 

 it was at first supposed would furnish good marks by 

 which to subdivide the genus into groups, proved other- 

 wise. The thickness of the bones of the skull is general- 

 ly correlated with other characters, rather thin papery 

 skulls bearing strongly developed bony ridges, while 

 thicker and more bony skulls have the ridges low or ob- 

 solete. But there are several exceptions to the rule. 

 Other characters at first seem important, but as they occur 



*Prof. Eigeumanu has changed the name of this ridge and its spine 

 from "occipital" to "parietal," and I have adopted his name for it, be- 

 cause it seems much more appropriate. 



