746 B. W. KUNKEL 



somewhat triangular, with the base posterior and apex in front. 

 This cartilago entoglossahs is imbedded in a much larger mass of 

 fibrous tissue in which some scattered cartilage cells are pres- 

 ent. In the adult, this siurounding mass of fibrous tissue forms 

 a conspicuous heart-shaped plate beneath the anterior end of 

 the corpus hyale. 



In the adult of Emys, as already known, the three pairs of 

 cornua are distinct from the corpus hyale and are connected with 

 it by connective tissue. Already in a yoiing individual with a 

 carapace length of 28 mm. the three paus of cornua are distinct 

 from the corpus although the cornu branchiale primum is the only 

 part of the hyobranchial arches which exhibits an ossification. 

 The cornu hyale becomes segmented from the corpus hyale 

 slightly earlier than does the cornu branchiale secundum; for 

 example, in an embryo with carapace length of 13.5 mm. the 

 separation of the cornu hyale is complete wliile the cornu bran- 

 chiale secundum is only partially separated. 



A separate epibranchiale primum (Siebenrock '99) is present 

 as a separate triangular cartilage lying dorsal to the extreme dis- 

 tal end of the cornu branchiale primum in an embryo having a 

 carapace 13.5 mm. long. It remains as a distinct cartilaginous 

 element in the adult. 



In the fully grown Emys the cornua and corpus hyale are ossi- 

 fied and only the processus hngualis, a small oval foramen in the 

 anterior part of the corpus, the extreme distal ends of the cornua 

 branchiaUa primum and secundum, and the epibranchiale primum 

 remain chondrified. 



The earUest portion of the hyobranchial apparatus to be laid 

 down in cartilage is the cornu branchiale primum which is already 

 chondrified in an embryo having a carapace length of 7 mm. 

 It likewise is the earhest to show signs of ossification. In the 

 embryo modelled, ossification has already begun in its middle 

 portion, a short distance behind the posterior margin of the 

 corpus hyale. The cornu hyale chondrifies later than the cor- 

 pus hyale and at essentially the same time as the cornu branchiale 

 secundum; so that in the stage modelled, although the body is 

 completely chondrified, the cornu hyale is represented by a sepa- 



