AFFINITIES OF RANA SUBSIGILLATA. 23 



ThK CHONDROCRANflUM. 



The nasal cartilages consist of a roundly-pointed nasal roof 

 above and a trifid sub-nasal lamina below. 



Small triangular prairhinals are attached to the septum nasi. 



The -palatine cartilages extend from the ethmoid to the maxillae, 

 and are not peculiar in any way. 



Owing to the thickness of the fronto-parietals and the extreme 

 delicacy of the chondrocranium, I have not satisfied myself as to 

 the size and exact positions of the fontanelles. It is clear, how- 

 ever, that there is a large median fontanelle, the anterior portion 

 of which is bordered by the ethmoid, which at this point has a 

 slightly bilobular tongue-shaped area carved out of it. The 

 posterior wall of the otic capsule is cartilaginous ; it is bounded 

 by the parasphenoid below and by the prootic above. 



The columella auris is strongly developed. The inter- and 

 medio-stapedial portions are not unusual in any way; the extra- 

 stapedial section is strongly developed and has a fan-shaped 

 terminal of considerable size, which is applied in an inverted 

 position to the tympanic membrane. The squamosal, at the 

 junction of the interior limb with its stem, forms a deep arch 

 over this delicate cartila.ge, and also gives support to the annulus 

 ti/mpaniciis, which is somewhat funnel-shaped, broader than deep, 

 and slightly notched above. 



The maxillary arch. 



The jKilatines are straight, semi-transparent hones, placed at 

 right angles to the axis of the skull. They do not meet each 

 other. 



The squamosals differ widely from those of Rana [sensu stricto). 

 They are enormously developed. The zygomatic branch, slightly 

 rugose, forms a suture with the maxilla which is prolonged for- 

 ward to the naso-palatine bar. This process tapei-s considerably 

 at its anterior end, and is about half the length of the entii'e 

 skull * ; the suture is about four-fifths of this length. The inner 

 limb, just over one-third the length of the zygomatic, with which 

 it forms a I'ight angle, is superimposed on the prootic, of which 

 but a small border is exposed on each side. The posterior limb, 

 or stem, of this bone is somewhat oblique, flat, and rounded at 

 its distal end ; it is applied to the pterygoid and the quadrate 

 cartilage. 



The pterygoids are the most remarkable bones in the skull. 

 The inner processes overlap the lateral processes of the para- 

 sphenoid almost to their junction with the blade -like portion. 

 At the junction of the anterior and posteiior limbs, and opposite 

 the root of the inteiior limb, is a large rounded process, which, 

 when the skull is in its natural position, is directed outwards and 



* Processes measured from their junction witli tlie sliaft of the bone, not from the 

 right angle where they join each other. 



