548 MR. D. W. DEVANESEN ON THE 



sternohyoideus proper) has clifFerentiated into two separate 

 muscles in this toad, one lying above the other. This differen- 

 tiation starts at the fourth and the last inscriptio-teiidina of the 

 Tectus-abdominis. A similar division of this muscle has been 

 observed in Breviceps and Hemisus by Beddard (1). What corre- 

 sponds to the "inner (median?) portion of the same muscle" 

 is a strip which arises entirely from the xiphisternal plate (text- 

 figs. 15, ST. I., & 16). Now, these three divisions of the sterno- 

 hyoideus are separately inserted on to the body of the hyoid, 

 one behind the other and in close succession ; none of the fibres, 

 however, is attached either to the posterior cartilaginous process 

 of the same hyoid plate or to the posterior cornu. 



On removing the hyoid portion of the inner genioglossus 

 muscles, the hyoglossus pair comes into view which, in turn, 

 conceals aiiother muscle in the ordinary position of dissection. 

 The thick, coarse fibres in the interior of the azygous portion of 

 the hyoglossus are either sinuous or twisted like a corkscrew. 

 As this muscle is the retractor of the tongue, this condition, at 

 rest, of the fibres mentioned suggests that they are capable of 

 being stretched to a greater extent than usual so as to permit 

 the tongue to reach a comparatively longer distance. In Rana 

 the paired portion of the same hyoglossus is the innermost 

 muscle in contact with the lower surface of the posterior cornua ; 

 but, in this toad, there intervenes a new pair of muscles between 

 the two, which arises from the distal quarter of the latter, and 

 is inserted to a strong fascia spreading in the space enclosed by 

 the proximal parts of the anterior cornua and the anterior 

 margin of the basi-hyal (text-fig. 16 C, C.H.). Among the muscles 

 connected with the hyoid skeleton, there are several which are 

 solely attached to the posterior cornua on the one side and to 

 the bones of the skull and of the pectoral girdle on the other. 

 Now, it is likely that this new muscle, which we may term the 

 comuoideus-posterior, counteracts a probably too powerful pull 

 of these muscles in question on the same cornua by binding the 

 latter with the basi-hyal plate, One finds another new pair of 

 muscles, not recorded in Rana, arising from the xiphisternum 

 and running forward beneath the auricle to be attached to the 

 posterior cornu (text-fig. 16 A, S.C.) ; this may be called the 

 sterno-Gornuoideus in accordance with its origin and insertion. 

 The petrohyoideus muscles are distinguished by their robust 

 development and by their numerous insertions. The petro- 

 hyoideus-anterior arises from the pro-otic by means of a single 

 tendon, and spreads over the outer surface of the pharynx, to 

 whose wall all its fibres are more or less adherent (text-fig. 1 6 A, 

 B, C, and D). According to the several insertions of this muscle, 

 one may recognise the following divisions: (1) a band, P. A. 1, 

 inserted on to the fascia in relation with the proximal parts of 

 the anterior cornua ; (2) another anterior portion, P, A. 2, attached 

 to the root of the same cornua; (3) a small narrow division, 

 P.A. 3, attached to the lower surface of the basi-hyal ; and (4) a 



