PRIMORDIAL CRANIUM OF THE CAT 367 



parable with the lamina parietahs of placental mammals, also 

 to the hinder portion of the taenia marginalis of Lacerta (Gaupp, 

 '08, b). 



Chondrification of the parietal plate independently of the ear 

 capsule was not observed in the series of Echidna studied by 

 Gaupp, but it was noted that the plate was separated from the 

 occipital pillar caudally and from the ala orbitalis rostrally by 

 stretches of unchondrified tissue. Noordenbos is apparently the 

 first to have observed the independent origin of the parietal plate 

 and its secondary union with other parts of the skull. In Talpa 

 of 11 mm. this cartilage was dorsad of the ear capsule and im- 

 mediately in front of the tectum interoccipitale; its union with 

 the otic capsule occurred very soon after its appearance. Evi- 

 dently the parietal plate in Talpa does not unite posteriorly with 

 the occipital arch, but with the tectum interoccipitale. The 

 latter appears in the mole at the same stage as does the parietal 

 plate, in the form of an independent piece arched over the cere- 

 bellar region. Noordenbos observed its union, first with the oc- 

 cipital arch, then considerably later with the parietal plate. On 

 account of the primary union with the occipital arch Noordenbos 

 is inclined to adopt the term 'tectum interoccipitale' as more cor- 

 rectly expressing its relations than the terms 'tectum synoticum' 

 and 'tectum posterius.' Whether the tectum arises by paired 

 anlagen in the mole could not be stated; its origin in the rabbit 

 was observed by Noordenbos to be paired. 



In regard to the origin of the parietal plate in cat, I am unable 

 to present a conclusion, owing to lack of material at a critical 

 stage in the development of this part. Apparently primary con- 

 ditions siiTiilar to those described for Talpa obtain in Felis. A 

 cartilage, which I have called lamina parietalis, arises by paired 

 beginnings in the form of triangular plates, above the interval 

 between the occipital arch and pars canalicularis. At a later 

 stage the parietal plate has united with the lateral occipital arch 

 and presents a prominent angle toward the mid-dorsal line, which 

 is the beginning of the tectum posterius. At this stage (15 mm.) 

 there is a faintly stained tract of cartilage in the region of the 

 future commissura orbito-parietalis, but extending caudad into 



