1878.] Development of the Skull in the Common Snake. 15 



" epi-hyal " (" hyo-mandibular "), which becomes tbe stem of tbe 

 " columella auris ;" but the " branchial" folds develop no cartilage in 

 them, and soon are lost in the sides of the neck. 



There is but little cartilage developed in the cranium. The ear- - 

 capsules are large, long, and become solid cartilage before they ossify, 

 and the simple nasal roofs chondrify and never ossify. 



There is a large cartilaginous occipital ring or arch, but the 

 sphenoidal regions, which have exceptionally autogenous alee, are very 

 feeble and small. 



The trabecular, which are manifestly mere outgrowths of the para- 

 choidal tracts, develop into long terete rods of cartilage, but do not 

 ossify at all in front of the pituitary space. 



They coalesce in the internasal region, and coalescing also with the 

 descending lamina? of each nasal roof-cartilage, they form a low septum 

 nasi. 



There are two pairs of " extra-visceral," or labial, cartilages. 



The "epi-hyal" rudiment coalesces during chondrification with the 

 stapedial plate ; it gives off a. small scale from its postero- superior 

 edge. This is a minute rudiment of the " stylo-hyal " element. 



Both in the cranium and face there is a copious growth of very per- 

 fect bone developed in the sub-cutaneous stroma. In the cranium the 

 frontals quite, and the parietals almost, meet below. Thus the trabe- 

 culge are excluded from taking part in the formation of the front part 

 of the cranial cavity. 



These rods lie in the grooved sides of the " parasphenoid, " which 

 has no basi- temporal part, as in the- bird, but becomes ankylosed to the 

 double, edosteal basi-sphenoid. 



These are some of the most striking points in the growing snake's 

 skull ; for the rest I must refer to the main paper. I may, however, 

 make a few remarks upon the " new things " to be seen in this low 

 sauropsidan skull. 



The occipital condyles are confluent at the mid-line, so as to form a 

 rounded single surface, with a dimpled middle part. 



The auditory capsule acquires three bony centres that do not unite 

 with each other, but with the nearest bones of the cranium. 



Thus the prootic coalesces with the alisphenoid, the epiotic with the 

 superoccipital, and the opisthotic with the exoccipital. 



The columella and stapes are one bone, not distinct as in the 

 batrachia. The union takes place very early. 



The mandible opens very far back, behind the occiput, and as the 

 quadrate passes over the stylo-hyal, the two become ankylosed together. 



For the palate a new bone appears, namely the " trans-palatine ; " 

 but the meso-pterygoid is not distinct from the pterygoid in the 

 ophidia. It occurs in Angtiis fragilis. 



The little " pre-orbitals " that in the Amphibia form a floor to the 



