The Amphibian larynx. 30Ô 



of general application to all the varying forms of the Anura, and 

 which may agree both with the morphological significance and the 

 physiological function. With consideration of the difficulties in the 

 way I may suggest the following: 



1. Derivatives of Dorso-branchialis ^ (D^) 



a. Petro-hyoideus^ (Eckek) P.h^ 



b. Dilatator aditus laryngis (Henle) t 



including the two slips differentiated jf 

 from this \t" 



2. Derivatives of the laryngeal ring. 



a. Sphincter laryngis (Göppert) S 



This name is to be used whenever the primitive ring or a 

 portion of it remains. 



In case its division into quadrants, the parts may be referred 

 to as Pars dorsalis (S-d) and Pars ventralis (S. v). 



b. Constrictor laryngis (Henle) Cs 



The muscle which differentiates from the ventral half of the 

 original Sphincter. This appears always to contract the 

 space enclosing the larynx, perhaps by approximating the 

 thyroid processes (Ecker). 



c. Compressor laryngis (Henle) Cp 



The counterpart of the preceding, differentiated from the 

 dorsal half of the Spincter. 



c) Comparison of different Anuran forms. 

 The Dilatator aditus laryngis is the most constant of all 

 the Anuran laryngeal muscles, and shows the least variation. In 

 Rana (Fig. 31) it is a thick band, slightly curved, arising from the 

 cartilaginous distal end of the thyroid process, and inserted into the 

 inner edge of the arytaenoids. In Bufo it is somewhat separated at 

 its orid» into two slips, owing to the singular development of the 

 Hyo-glossus, which is, at its origin, reflected around the thyroid pro- 

 cess. In the Eylidae it is excessively wide, sometimes even wider 

 than long (Fig. 52, Chorophilus and Fig. 56, Hylodes), and is apt to 

 become fan-shaped. In the aberrant Bombinator (Figs. 45 — 47) it is 

 perfectly normal in origin and insertion, although it is reduced to a 

 narrow ribbon. In Bactylethra there seems to be a complex muscle 

 mass arising from dijfferent portions of the hyo-laryngeal resonance 

 box (Fig. 58) but I am unable to give particulars concerning this, as 

 my only material consists of a series of sketches drawn from a spe- 

 cimen dissected several years before. The most anterior of these 

 elements {t in Fig. 61) appears closely to resemble the Dilatator of 



21* 



