688 MR FRANK J. COLE 



The tentaculo-ethmoidalis lies internal and somewhat dorsal to the transversus oris, 

 and in fact in dissection (except in Perenyi material) there is some difficulty in satis- 

 factorily separating them, as mentioned by P. Furbringer. J. Muller evidently 

 had this experience also, for he fails to distinguish between the two muscles, and 

 describes them together under the name given above. The sections, however, 

 demonstrate conclusively their complete independence. 



From its origin the muscle courses backwards and outwards, wedged in between 

 the copulo-ethmoidalis and the transversus oris, its fibres diverging ventro-dorsally 

 like a fan, to terminate, after a short course, on the external lateral fascia between the 

 two muscles just mentioned above in front of the base of the third tentacle and in 

 front of the posterior vertical portion of the lateral labial cartilage. P. Furbrinuer 

 asserts that it is inserted into the base of the third tentacle, but I find no evidence of 

 this in dissections, and it is certainly not the case in the sections. 



5. M. transversus oris. (Figs. 3, 10, 11, t.o.) 

 J. Muller (in part), Compressor des Mundes, Mundschliesser (p. 259). 



A complex and diffuse muscle, as defined by J. Muller and P. Furbringer, and 

 said by Allis to consist in Bdellostoma of "two transverse subnasal muscles." In 

 dissections a division of the muscle into two parts seems to be indicated in Myxine also, 

 although not mentioned by P. Furbringer, but a complete separation is not possible, 

 and the sections show that the division is not a real one. Perhaps the two transverse 

 muscles mentioned by Allis are the two commissures described below from the sections 

 (cp. fig. 10), in which case he does not include the greater part of the transversus oris 

 of other authors. 



I find some difficulty in reconciling my descriptions of this muscle based on 

 dissections and on the sections. This may be, and perhaps is, due to the fact that it is 

 difficult in dissections, however careful, to correctly define a small and irregular muscle 

 closely packed up with and attached to other tissues in a confined space. On the other 

 hand, the sections fail to convey a clear impression of the ensemble of the muscle, and 

 then, again, the muscle may vary considerably. I have therefore thought it advisable to 

 give two descriptions, one of a careful dissection of a 34|- cm. Hag, and the other based 

 on my large series of sections. 



It will be convenient in the description of the dissection to divide the muscle into 

 two regions, although, as stated above, this division is not sanctioned by the sections. 



Posterior Region. — Lies, in a lateral view, apparently immediately in front of the 

 tentaculo-ethmoidalis, to which it is somewhat closely attached, and seems to be quite 

 distinct from the anterior region. This, however, is really due to the fact that many 

 of the fibres, and especially the dorsal ones, are less transverse than those of the latter 

 region. In the present specimen (see fig. 3) the most dorso-superficial fibres of the 



