SPECIAL DISCUSSIONS AND DESCRIPTIONS. 



HOLOCEPHALA. 



Holocephala Miiller, 1835, Vergleiohendo Analomie der Myxinoiden, 10. 



Of the occurrence of species belonging to this group in the region 

 traversed by the expedition there can be little doubt; they occur at a 

 comparatively short distance to tlie north and to the south, yet the 

 absence of representatives in the material under examination limits the 

 discussion in these pages to matters pertaining to the group in general 

 as inhabitants of great depths. 



One species of the genus Chbnaera Linne, 1758, C. inonstrosa L., has 

 been noted by Vaillant, 1888, from a depth of 687 fathoms, off the Azores, 

 and another species, C. affinis Capello, more often taken at great deptlis on 

 both sides of the north Atlantic, is given by Giinther, 1887, a range from 

 200 to 1200 fathoms, or by Vaillant to 1285. An egg referred to C. 

 monstrosa by Alcock, 1892, from a depth of 410 fathoms, off the Coroman- 

 del Coast, probably belongs to a new species. Chimaera Colliei Lay and 

 Bennett, 1839, is a shoal water fish that descends to depths of a hundred 

 fathoms or more at particular seasons, off the coast of California. By 

 some mistake the figure of this fish in the Zoology of Beechey's Voyage, 

 Fishes, Plate XXIII., fig. 1, has been copied in the " Oceanic Ichthyology," 

 Plate X., fig. 30 as " Callorhi/nchus anfarcJicus." So far as now known, the 

 species of Callorhynchus have habits similar to those of Chimaera Colliei; 

 though the specimens secured have been taken at moderate depths, the 

 species in all likelihood retreats at certain times to greater depths, as is 

 the case with most Selachians and Fishes. It will be evident on compari- 

 son with the egg figured below, Plate LXIV., fig. 2, as that of Callor/ii/nc/ius 

 antarcticus, that Giinther is probably correct in identifying the egg figured 

 by J. Miiller, 1842, Ueb. den Glatten Hai, Taf. 6, fig. 3, and that figured 

 by Dumeril, 1865, Poiss., I., PI. 8, fig. 8, as eggs of Callorhynchus, the 



