294 ALUS. [Vol. XVIII. 



in the nomenclature and numbering employed by me in my descrip- 

 tions of Amia (No. 4, p. 720), a postoccipital, or first spinal 

 nerve, and not an occipital nerve. This has been already fully 

 set forth in an earlier work (No. 6), but can be briefly summar- 

 ized here. In the nomenclature employed by Fiirbringer (No. 

 25) the third occipital nerve of Scomber must be either nerve 

 "c," or nerve "d," for it issues through the skull and the nerve 

 next posterior to it is the first free spinal nerve. If it be nerve 

 "c," the anterior occipital nerve of Scomber would be nerve "a," 

 a nerve which, according to Fiirbringer, has never yet been ob- 

 served in any teleost. If it be considered as nerve " d" 

 instead of as nerve '" c," Scomber would still seem to form an 

 exception to all teleosts in that this nerve traverses an occipital 

 foramen, for the nerve next posterior to nerve "c" is, in all the 

 teleosts described by Fiirbringer, said to be nerve 4, and the nerves 

 so designated are said to be the first free spinal nerves. In cer- 

 tain fishes this nerve 4 is said by Fiirbringer, to issue with nerve 

 "c" from the cerebrospinal canal; but as, in the fishes in which 

 this is said to occur, the second occipital arch is said to have dis- 

 appeared, this would seem to indicate that the two nerves did not 

 either of them perforate, in any part, the skull. 



In Amia the first free vertebra gives attachment to the sixth 

 intermuscular septum. In Scomber it gives attachment to the 

 fourth. In Amia there are, anterior to this first vertebral or 

 sixth intermuscular septum, one free spinal nerve, two spinal-like 

 nerves with dorsal and ventral roots, and two with ventral roots 

 only. In Scomber there are, anterior to the first vertebral septum, 

 three spinal-like nerves, two of them having both dorsal and 

 ventral roots, and one of them a ventral root only. The anterior 

 muscle segment in each fish has no corresponding nerve. There 

 are thus, in Amia, in front of the first free vertebra, two more 

 muscle segments and two more spinal-like nerves than there are 

 in Scomber. This, taken together with the relations of the several 

 nerves to the pectoral fin, to the clavicle, and to the trunk muscles 

 arising from that bone, and also the relations of the septa and 

 muscle segments to the skull and to the dermal bones of the 

 region, all seem to indicate that the two occipital vertebrae found 

 partly fused with the hind end of the skull in Amia, are found as 

 the first two free vertebrae in Scomber. 



