412 H. B. POLLARD, 



a forameu (iu Siredon between the dentary and opercular) and then 

 supplies the Mylohyoid." 



"This brauch is the Ramus circuintiexus, aud iu the Frog it alone 

 forms the terminal portiou of the lufrumaxillaris" (Gaupp). 



The R. submaudibularis is present iu Myxinoids, running however 

 along with the mentalis outside the Processus coronoideus and sup- 

 plying the skin in front of the Meckclian cartilage. This branch pos- 

 sesses a certain resemblance to the Ramus maudibularis externus but 

 nevertheless it appears to me to be really the submandibular, 



Meckclian Cartilage. 



The Meckclian cartilage of Trichomycterus is of an irregular in- 

 verted T shape, the crossbar of the T being horizontal, the corouoid 

 process representing the stem. The process towards the quadrate 

 does not reach the articulation, partly because the cartilage, even at 

 this young stage, has been resorbed after the formation of the os 

 articulare. Probably at no ontogenetic stage was this arm at all 

 massive. The mentomeckelian process is also very short and far from 

 reaching the symphysis, that being formed by the dentary bones only. 

 The Processus corouoideus proceeds upwards and forwards accompanied 

 by boue. It bears the procartilagiuous corouoid piece. The demarca- 

 tion between the hyaline cartilage of the corouoid process and the 

 procartilage of the corouoid piece is quite clear. 



In Callichthys the corouoid process is wanting, and the corouoid 

 piece is rudimentary. The mentomeckelian extends very little forwards 

 and to judge from the appearance of the cartilage there has been no 

 resorption, so that probably it never extended further at earlier stages 

 of its ontogeny. The mentomeckelian processes are as far from 

 reaching the symphysis as in Trichomycterus. 



In Auchenaspis the condition is a little different from that of 

 Trichomycterus. The posterior arm is in the same state aud the 

 processus coronoideus passes up, aud bears the corouoid piece. The 

 mentomeckelian process is however longer, reaching halfway from the 

 corouoid process to the symphysis, taperiug away. 



In Silurus, where the cartilage is more extensively present, the 

 posterior arm extends beyond the articulation with the quadrate , as 

 an angular process, and the mentomeckelian process is fused with its 

 fellow and the symphysis. In Hypostomidae the whole rami of the 

 lower jaw may be said to be free, there being no sym])hysis. A i)ro- 

 ccissus corouoideus is stated to be frequently present iu lish by Stan- 



