DR. J. MURIE ON THE ORGANIZATION OF THE CAAING WHALE. 2635 
broadly with an anterior protuberant blunt corner 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 thyroid 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 sterno- 
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 sterno-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 forwards, 
is fixed 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.8. 1867, p. 480. * Trans. Roy. Soc. 1868, p. 219. 
* Balenoptera, l.c. p. 237. 
* Not mentioned by these authors ibid., but both described by Stannius, ‘ Miill. Archiy,’ 1849. 
