624 
F. H. EDGEWOETH. 
present in Myrinecophaga, Tatasia^ Dasypus villosus. In 
Tolypeutes tricinctus a tendinous inscription is present 
between the anterior and posterior portions, and is attached to 
the hyoid. A sterno-hyoideiis lies dorsal to the posterior portion. 
The posterior digastric ends in a transverse aponeurosis in 
intimate connection with the posterior margin of the inter- 
mandibularis. In Brady pus tridactylus there is a tendinous 
inscription ; the anterior portion forms an anterior digastric 
and the posterior portion a true sterno-hyoideus in that whilst 
its median portion is attached to the inscription its lateral 
portion is attached to the first branchial bar. The posterior 
digastric is attached to the lateral end of the inscription. A 
digastric muscle is thus formed. This condition is one inter- 
mediate between those described above and that found in 
high er ]\I a m mals . 
The following observations bear on this question. lu 
embryos of Amphibia and Sauropsida, and also in the rabbit 
and pig, the hypobranchial spinal muscles — formed by down- 
growtlis from two or more anterior body myotonies — form a 
longitudinal cell column, the anterior end of which, growing- 
forward dorsal to the inter-hyoideuss. hyoid ventral constrictor 
and intermandibularis to the front end of MeckeTs cartilage, 
divides into two at the level of the second or first branchial 
cartilage, the part in front forming the geuio-hyoid, the part 
behind the sternodiyoid. In the rabbit and pig this primitive 
sterno-hyoid develops into sterno-hyoid, sterno-thyroid, 
thyro-hyoid, omo-hyoid.^ 
It would follow that any connection of the anterior end of 
the sterno-hyoid with a muscle lying ventral to the inter- 
mandibularis s. mylohyoid is a secondary phenomenon. 
F urther, in a 30 mm. embryo of Dasypus n o v e m c i n c t u s 
the following condition was found : The sterno-mandibularis 
had a tendinous intersection at the level of the hind edge of the 
intermandibularis. The sterno-thyroid was attached to the 
basibranchial and thyroid cartilage by two separate slips. 
A thyro-hyoid extended from the thyroid to the first branchial 
^ Details of this development will be given in a later paper. 
