ON THE GENERAL MORPHOLOGY OE THE MYXINOID FISHES. 675 



In my large series of sections there are some independent nodules of soft cartilage 

 in the " branchial " arch region which may be mentioned here. One of these is situated 

 dorsally in the neighbourhood of the free extremity of the superior lateral cartilage 

 (s. I. c), and was only present on the left side (cp. figs. 1 and 2). Another is ventral, 

 is associated with the tip of the lower division of the second "branchial" arch, and is 

 present on both sides, as shown in the figures, although more marked on the right. 

 As we know from Stockard's work (30) that immediately posterior to the mouth cleft 

 there are three pairs of clefts which disappear during embryonic development, it is 

 possible that these remnants may represent a third " branchial " arch. 



The so-called " hyoid" arch (hy.) is more accurately figured in the present part than 

 in my first. The forwardly projecting ventral plate which was formerly referred to 

 as a variation I now believe to be a normal structure. It consists of soft cartilage, is 

 very thin, and strips off with the slightest tension in cleaning up the skeleton. The 

 ventral edge of the hyoid may also be ragged — in the charts this is more noticeable on 

 the left than on the right side (cp. fig. 2). The projections into the third and fourth 

 fenestrae are pointed, and it is interesting to note on the right side that the " hyoid " 

 arch, owing to a postero-dorsal extension of the third fenestra, only remains con- 

 nected with the superior lateral cartilage by a narrow bridge (fig. 2). It is possible 

 this may represent one of the breaks present in the embryonic skeleton. 



The anterior fusion of the palatine bars (pi.), known as the palatine commissure, is 

 coloured red in fig. 2, although it consists by no means entirely of hard cartilage. There 

 is, in fact, a considerable infiltration of soft cartilage here, and as Parker describes a 

 definite tract of soft cartilage in the commissure which he calls the " ethmoidal region," 

 it is possible the soft infiltration may appear on the surface as a well-defined area in 

 some specimens. In his sections Parker colours the " ethmoid " as hard cartilage, and 

 explains that the sections being taken from an older animal the hard cartilage had 

 replaced the soft. 



I have previously referred (7, p. 765 ; 8, pp. 694-5) to a median pad of soft 

 pseudo-cartilage immediately in front of the palatine commissure and the median 

 dorsal tooth. Although the two palato-ethmoidalis profundus muscles are closely 

 opposed to this pad, they are not, I believe, as I formerly stated (7), attached to it. 

 Shaffkr refers to this structure in the following terms (p. 250): " Als selbstandige 

 knorpelige Masse findet man dieses Gewebe [pseudo-cartilage] weiter in Form eines 

 horizontal und quer gelagerten Stabchens vor und unter der vorderen Vereinigung der 

 Gaumenleisten, welches sich caudad in zwei langliche, im Querschnitt rundliche 

 Fortsatze gabelt ; letztere umfassen die Basis des Gaumenzahns." 



The cornual cartilage (c. c.) exhibits a feature which I believe to be always present, 

 but which has hitherto escaped attention (cp. 7, p. 766). I refer to the backward and 

 inward projection from the cartilage near its tip, and which is connected by a short, 

 stout ligament with the lateral labial cartilage shortly behind where the latter fuses 

 with the cartilage of the third tentacle (figs. 1 and 2). J. Muller figures a connection 



