690 MR FRANK J. COLE 



again becomes increasingly evident on the surface, both laterally and ventrally, and 

 continues so for the remainder of its course ; and as the tentaculo-ethmoidalis narrows 

 down in front, the transversus oris expands in the transverse plane. The dorso-intenial 

 fibres now pass upwards, and are inserted (? origin) into the entire internal surface of 

 the sheath of the first tentacular cartilage after the latter has entered the contour of 

 the snout, whilst the remaining fibres pass straight forwards and are inserted into the 

 dorso-external surface of the sheath of the second tentacular cartilage, also within the 

 contour of the snout ( = transverse labial cartilage). 



As far as the sections are concerned, the above represents a clearly defined and 

 independent muscle, the object of which is to assist in the varied movements of the 

 first and second tentacles. It therefore may be said to represent the transversus oris 

 sensu stricto, although, of course, it is not a transverse muscle. There are, however, 

 closely associated with it, two other muscle bundles, each of them strictly a separate 

 muscle, but which I describe here, as they are evidently all included under P. 

 Furbringer's transversus oris. The independence of these and other muscles will be 

 reconsidered in the concluding morphological part of this work. 



Ventral Commissure (fig. 10). — Arises as follows : — (a) some fibres from the ventro- 

 internal surface of the sheath of the root of the second tentacular cartilage (trans- 

 verse labial) ; (b) a few fibres from the internal fascia of the anterior division of the 

 copulo-tentaculo-coronarius ; (c) the majority of the fibres from the ventro-internai 

 fascia of the transversus oris, sensu stricto. I do not think the latter muscle con- 

 tributes any fibres direct to this commissure, but the association between them is very 

 close. This transverse commissure is seen on the ventral surface at the anterior end 

 of the snout on removal of the skin, and passes without a break from the origin of one 

 side to that of the other, ventral to the transverse labial cartilage and the anterior 

 extremity of the tentaculo-ethmoidalis. 



Dorsal Pseudo- Commissure. — I thought at first that this was another true 

 transverse commissure, but a careful examination of the sections reveals that the two 

 muscles only meet at a median linea, and that no fibres pass continuously from one 

 side to the other. It " arises " from the dorso- internal surface of the sheath of the 

 root of the second tentacular cartilage (transverse labial), and passes downwards, 

 backwards, and inwards, at first lying over and closely associated with the ventral 

 commissure, and immediately below the nasal tube. It, however, extends further 

 back than the ventral commissure, so that it crosses the latter diagonally and appears 

 by itself behind it. The two muscles meet at an angle at a connective tissue linea 

 situated at the middle line just below the nasal tube. As the transverse labials pass 

 backwards to fuse at the median line with the subnasal bar, the pseudo-commissure 

 lies dorsal to them, and the more posterior fibres are "inserted" into their dorsal 

 surface at the point of fusion not far from the middle line. 



The transversus oris is not separated by J. Muller, who confuses and describes it 



