J. K. Thacher — Median and Paired Fins. 305 



The aborad four (12-15) branches, coming directly from the 

 myelon, advance, each by itself, close to the metai)teryoiuni, where 

 they each bifurcate, sending one branch to the dorsal and the other 

 to the ventral side of the tin. The next four (S-11) unite to form a 

 rather loose plexus, which separates again into four nerves, wiiich 

 then sub-divide in the same way as the last mentioned four, except 

 that the orad of these behaves a trifle differently in a manner here- 

 after to be described. 



Now the first seven nerves unite with one another and with the 

 minute branch of the vagus in the following way. The vagal branch 

 emerges from the skull with that nerve, but already rolled up as a 

 separate branch and easily to be separated from it; this joins the 

 first myelonal nerve and this the second, and their sum the third, and 

 so on, until we have a cord formed of the vagal and first seven 

 myelonal branches. This sends ofi' a branch to the muscles and 

 integument in front of the shoulder girdle, but the main part of it 

 proceeds on its way to enter the foramen called by Gegenbaur, 

 liiintriUsoffming^ and then divides within the cartilage of the girdle 

 in the way which he has described, and similarly to the aborad nerves 

 which he has left unnoticed, sending one branch to the dorsal and the 

 other to the ventral muscles of the fin. Now the eighth nerve sends 

 off its ventral branch like those aborad of it, but the dorsal branch 

 enters the entrance-opening with the cord of the vagus and 1-7 spinal 

 nerves; but it does not unite with this cord till after the latter has 

 divided, and then unites with its dorsal branch and emerges with that 

 from the cartilage on the dorsal side of the fin. In another specimen, 

 this dorsal branch of the eighth nerve enters the cartilage by a minute 

 separate foramen, but unites with the dorsal branch of the anterior 

 cord, as in this case. 



As stated, my observations in the other cases have not been as 

 thorough, and I cannot give the number of ner\es, but in the ventral 

 fin the arrangement is as follows. A number of nerves are gathered 

 together to form the orad cord. This, on coming opposite the fora- 

 men in the pelvic girdle, divides and sends its branch to the ventr^il 

 side of the fin through that. Then the other aborad nerves coming 

 out, each by itself, to the metapterygium divide into two branches for 

 the two sides of the fin, just as in the case of the pectoral fin. This 

 is in 3Iustehis canis. 



In Eugomphodus Htor(dls, see PI. LX, fig. 00, from the articulation 

 of two or three rays with the girdle, aborad of those which by their 

 concrescence mark themselves out as the pro])terygiuni, it appears 



Trans. Conn. Acad., Vol. HI. 39 February, 1877. 



