ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 727 



middle line in the specimen now described, and over its last 16 mm. I have never 

 seen the fibres of this division inserted into the protruding end of the longitudinalis 

 linguse. In most dissections, and also in the sections (cp. fig. 2), the posterior fibres 

 of this division were the direct continuation of the dorsal fibres of the constrictor of 

 the gills. If, therefore, in fig. 3 the ligamentous area between these two muscles 

 remained muscular, and there was hence no origin from the dorsal fascia, this con- 

 dition would be reproduced. In other words, the posterior fibres, instead of arising 

 from the dorsal superficial internal fascia, more usually course longitudinally at the 

 side of the gut, and are unquestionably simply the continuation forwards of the dorsal 

 fibres of the constrictor of the gills, and, strictly speaking, are a part of that extra- 

 ordinary muscle. This, as above mentioned, is borne out exactly in the sections, where 

 the most posterior bundle of the constrictor pharyngis is clearly a portion of the 

 constrictor of the gills, and constitutes the first loop of this muscle in connection with 

 the first gill sack (cp. the Chart, fig. 2). The ligamentous sheet referred to above is 

 absent. 



The bearing of these facts on the question of the morphology of the constrictor 

 pharyngis is discussed in the section on the constrictor of the gills, and we need only 

 note here that the absence of any means of distinction between these two muscles 

 indicates that they are essentially parts of one and the same branchial muscle, which, 

 on the loss of the anterior gills, became modified in front as the constrictor pharyngis. 



The first part of J. Muller's constrictor of the pharynx = my cranio-hyoideus. His 

 second and third parts = part I. of my C. pharyngis. The second part of the latter 

 muscle in Myxine is thus absent in Bdellostoma, judging from J. Muller's description, 

 whilst the third section in Myxine (at least in part) = J. Muller's first loop of the 

 constrictor of the gills in Bdellostoma. 



It is stated that the constrictor pharyngis, by drawing the basal plate and " tongue " 

 muscle complex upwards and backwards, presses the gut against the parietalis and 

 notochord, and thus occludes it. 



29. M. constrictor branchiarum et cardise, F.J.C. (Figs. 2, 3, 13, c. b. c, c. b. c'., 



c.b.c"., numerals 1-1 4). 



J. MiiLLBR, Constrictor der Athemorgane + Constrictor (Sphincter) der Cardia (Constrictor 

 cardise) (pp. 270 and 273). Constrictor der Kiemen und der Cardia (p. 328). 



As the above two muscles of J. Muller are both parts of one series, I propose to 

 consider them together under the above name. Further, my description of this muscle 

 is based largely upon dissections, as a detailed reconstruction of this maze from the 

 sections, after spending the whole of one long vacation in repeatedly dissecting it, was 

 a Quixotic task I had not the courage to face. I have, however, prepared a chart which 

 illustrates the general anatomy of the muscle in the sections, a few notes on which will 

 be appended to the present description. 



