204 BULLETIN OF THE 



His figures on Taf. XVII. Figs. 306, 317, and 316 a, c, of frontal sec 

 tions from embryos of Bombinator igneus show that the aortic roots 

 anastomose by means of transverse vessels, and that at an early stage 

 of development there is an anterior (median) prolongation of the dorsal 

 aorta between and beyond the aortic roots ! How long this remnant 

 persists is not stated by the author. 



A series of transsections (see Figs. 5 a to 5 g) through the basis 

 cranii of Chlamydoselachus in the regions designated below as 1, 2, 

 and 3 (see Figure 1) gave the relations of the chorda and aorta to 

 each other shown in the following table. The distances refer to meas- 

 urements in the perpendicular to the long axis of the animal. The 

 sections were taken from three portions of the basis cranii containing 

 the structures cut from the vertebral junction, middle distance, and the 

 pituitary region respectively, the last piece containing the whole of 

 the " Sattellehne " and the pituitary space, with the foramina of en- 

 trance of the carotid arteries and the transverse canal. 



TABLE OF RELATIONS OF CHORDA AND AORTA, 

 (c = chorda, a = aorta.) 

 ( 1 ) From the vertebral junction. 



in middle of section. 



below and entirely outside basis cranii. 



( c ii 

 Section No. 1 :j , 



( c, the same as No. 1. 

 (a, 



c in middle of section. 



a inside cartillage, but on lower boundary. 



c in upper half, 

 in middle of lower quarter. 



c in upper half. 



4' 



{: 



5 



a in middle of lower half, 



■{: 



c in upper half. 



in upper quarter of lower half. 



From this point on, the rise of the aorta is very gradual until the section 



( 2 ) from middle distance between occipital region and pituitary space is 



reached, when in 



upper third of section. 



the middle of section. 



c in upper quarter of upper half. 



in middle of section. 



( r, the same as No. 2'. 

 3' < - 



°{: 



Section No. V \ cm 

 (a in 



( c in 



" " 2' -i . 

 (an 



I a, 

 <c, " 

 la, 



