214 MR. G. P. MUDGE ON THE MYOLOGY 



variations indicative of these more markedly than others, and tliat the Loriidae have 

 advanced fartliest ah)ng the road of specialization. These structural modifications 

 are such that a series of f^raded stages, starting IVoni tlie nio.st jjrimitive form uiul 

 ending with the most specialized, can be determined. 



Part II.— DESCRIPTION AND COMPARISON OF THE MUSCLES. 



Ceratoglossus Muscle. 

 (a) Inferior Ceratoglossus [hasio-glossKS of Nitzsch). — This muscle exhibits a series 

 of graded variations, and in one or two instances the variations are manifested among 

 the species of the same genus and even upon either side of the same tongue. A 

 comparison of its chief structural features shows that nine stages in the evolution of 

 the muscle may be made out [infra, pp. 266 & 268), and that there are two types of 

 structuie, which I propose to call the " unipars " and " duopars " type. The unipars 

 type is typically represented in the first stage, the duopars type in the highest stages, 

 and the gradations from the one to the other in the intermediate stages. 



Stage 1. 



The most primitive form of the muscle is exhibited in Cacatua alba. It is inserted 

 tendinous into the anterior lateral process of the os entoglossum, and arises fleshy from 

 the posterior border of the basihyal and the margin of the whole length of the urohyal. 

 Its general relations may be tinderstood by reference to PL XXVIII. fig. 25, which 

 represents its condition in Cacatua galerita. In particular, the extension of the 

 muscular origin along the urohyal (UR.) appears to be a most primitive character, and 

 in C. alba, C. sulplmrea, and C. trifon this is more strongly developed than in any 

 other Parrot, extending as it does to the extremity of the bony portion. In C. alba 

 the belly of this particular inner portion (cg.i.a^.) of the muscle is more strongly 

 developed than in any other species of Cacatua, the muscle of either side meeting each 

 other, but not uniting, in the middle line considerably forwards, and remaining in 

 contact throughout the remainder of their course backward to the extremity of their 

 origin. The inner portion of the muscle is not in any way separated from the outer 

 portion [cg.i.a.) as is partially the case in C. galerita, though there is a shallow groove 

 indicative of the first stage towards the attainment of this condition. I propose to 

 distinguish the whole of this muscle, which is almost exclusively related to the 

 basihyal and entoglossum, and only extends backwards upon the hypobranchial as far 

 as its head, as the ceratoglossus inferior anticus {cg.i.a.). 



There is given off from the ventral surface of the outer portion of the muscle a 

 muscular slip (cg.i'^.), which passes backward and becomes attached to a transverse 

 tendon {u.ten.) that passes from the lurohyal to the head of the hjpobranchial. 



