720 MR FRANK J. COLE 



origin as follows : — (a) from the skeletogenous layer of the lateral wall of the 

 membranous cranium just external to the massed cranial ganglia (which lie in a 

 space produced by the separation of the two layers constituting the cranial wall), 

 commencing at its anterior end immediately behind the eye, and passing backwards in 

 a descending curve on to the root of the superior process of the pterygo-quadrate. 

 Some of the deeper fibres in front arose in a dissection (but not in the sections) from 

 the anterior process of the pterygo-quadrate. This part of the origin was not found 

 by P. Furbringer. On the right side, in my large series of sections, the origin 

 extended further forwards so as just to cover and obscure the eye — here arising from 

 the optic capsule ; (b) the origin now extends vertically downwards in a curve over 

 the external surface of the central portion of the pterygo-quadrate on to the root of 

 the inferior process of the same, from the external ventral surface of the entire length 

 of which latter it also arises ; (c) the origin is finally continued backwards across the 

 hyoid (immediately above the ventral zone of soft cartilage in front), and then rises 

 slightly so as to pass over the posterior flat process of the hyoid, here lying internal 

 to the cranio-hyoideus. A few fibres arose from the root of the inferior lateral 

 cartilage, as stated by P. Furbringer. In the large series of sections the origin did 

 not rise on to the posterior flat process of the hyoid, but passed straight on to the 

 dorso-external surface of the root of the inferior lateral cartilage, and terminated 

 directly the latter was separated off from the hyoid. 



The fibres of the copulo-quadratus profundus course downwards and forwards in large 

 fasciculi, only slightly converging, and are inserted into the lateral (dorsal) margin of 

 the external bar of the anterior segment of the basal plate throughout its entire 

 extent. A few fibres were inserted into the pad of soft pseudo-cartilage at the 

 anterior end of the external bar, and a few also into the lateral margin of the anterior 

 end of the middle segment. P. Furbringer states that it is inserted into the anterior 

 third of the latter. 



In the sections, the insertion into the external bar was carried anteriorly to 

 immediately behind the fusion of the lateral labial with the external bar. In order to 

 reach the latter, these anterior fibres had to pass over the external surface of the 

 posterior extremity of the pad of soft pseudo-cartilage (cp. Part I., fig. 1), but I 

 think few, if any, fibres were inserted into it. Posteriorly, in the sections, the 

 insertion was carried over the pad of soft pseudo-cartilage between the external bar and 

 the middle segment of the basal plate on to the lateral margin of the anterior fourth 

 of the latter. 



The function of the copulo-quadratus profundus is to draw the basal plate (and 

 hence the ventral margin of the mouth) upwards and backwards, and in this way to 

 widen the mouth cavity laterally. 



