DE. J. MUEIE ON THE OEaANIZATION OP THE CAAING WHALE. 263 



broadly with an anterior protuberant blunt comer superior cornu. Posteriorly the wing 

 sweeps backwards and inwards in a long limb, the inferior cornu, which terminally 

 narrows and is fastened to the side and hinder margin of the cricoid cartilage. Between 

 the inner edge of the posterior or inferior thyroidal cornu is a large oval space, partially 

 occupied by the thyro-arytenoid and crico-arytenoideus lateralis muscles. The posterior 

 surface of the cricoid has a considerable arched expanse, and is a trifle longer than the 

 body of the thyroid cartilage. Behind, it is deeply incised or bifid, as Jackson specifies ; 

 in front, at the junction of the arytenoids, more abruptly transverse. Anteriorly the 

 cricoid, like the thyroid cartilage, sends off a pair of cornua, but which proceed in an 

 opposite direction, pass through the lateral thyroidal spaces, and, rounding the edges of 

 the body of the thyi-oid cartilage, embrace the trachea in front. These cricoid limbs, 

 or rods, well nigh meet in the middle line, and maintain a fair thickness throughout. 



A strong crescentiform sheet of ligamentous membrane unites the thyroid body and 

 thyrohyal bone. Another expanded sheet connects the latter, the basi-, cerato-, and 

 stylohyals ; both membranes have fleshy fasicles overlying them. 



Besides the muscles, chiefly protractors, having attachment to the hyoidean apparatus, 

 and which I have incidentally mentioned along with those of the tongue &c., the stemo- 

 hyoidei and thyroidei are two most powerful agents influencing retraction. The former, 

 broad throughout, widen as they are inserted into the basi- and thyrohyals. The latter 

 are not nearly so voluminous, and more ribband-like in figure. Their origin, as Mac- 

 alister' observes, is from the first costal cartilage as well as sternum ; their insertion, 

 side of thyroid cartilage. The stemo-thyroidei are wanting in B. rostrata'^, but are cer- 

 tainly present in several other forms of Cete. 



The thyro-hyoidei broadly cover the under surface of the thyroid cartilage and the 

 thyro-hyoidean membrane. Each crico-thyroideus, fleshy, and of considerable size, is 

 attached to the inner border and anterior surface of the cricoid cartilage and lower 

 border of the lateral horn ; thence it reaches the inner border of the inferior thyroidean 

 cornu. 



Upon the back or deep surface of the cricoid and posterior root of the arytenoid 

 cartilages a sheet of muscular fibres exists (fig. 13). From the devious direction of 

 these, more than actual division, two muscles on each side may be noted, the posterior 

 crico-arytenoid^ and lateral crico-arytenoid*. The former, probably the stronger and 

 larger moiety, overlays the dorsum of the cricoid, and, directed outwards and fonvards, 

 is fijxed to the root and posterior half of the arytenoid cartilage. The latter lies more 

 to the side, and, besides covering the cricoid laterally, has a partial origin from the 

 inner edge of the inferior thyroid cornu ; its fibres converge upwards and forwards to 

 the lateral root of the arytenoid in union with the former muscle. A well-defined, 



' P. Z. S. 1867, p. 480. » Trans. Eoy. Soc. 1868, p. 219. 



^ Balcenoptera, 1. c. p. 237. 



* Not mentioned by these authors ibid., but both described by Stannius, ' MiiU. Archiv,' 1849. 



