362 



Bashford Deo.': yriemorial Volume 



Text-figure 27- Text-figure 28. 



D;:£il and ventral views of the visceral skeleton of the notidanid shark, Heptanchus. 



Text-figure 27. Branchial skeleton o: Hioz^nchus sp., in dorsal view?. 



I-Vn, first to seventh tonchial arches; C, copula cr riiih'::i: _r. :ji.ei siyr.'z iri i- 

 . to fifth hasitenchEls; fey, ceiatohyoid; 1, hypobrir.;:n!;: J. :eri::rri=:h:£=: j, e 



.After (^er-riur. IS":, Fig. 1. Taf. XVm 



Text-figure 2S. \":j:e-l skele::' :: H:p--:h:,s ■-.s.z-^. 



bfc.2, second basilKaDchial; ;-... rjii- .;:_. jr.. :eri:cirir.c:.iili. :-... :eri:;hy:;i: ^,; 



After Daniel, 1934= Kg. 50.A. 



ventral aspect. 

 robranchials; mp., median piece. 



The vestigial seventh branchial arch in ChIa7n;ydoseI^u:hM^ was first described and 



figured by Fiirbringer 1903. p. 409 and Fig. IS, pi. X\''ir. In his specimen it consisted 

 of a single small rod or cartilage on each side. In a young specimen described by Hawkes 

 (1907) it consisted of four small pieces on one side and two on the other. In another 

 specimen, an adult, examined by Hawkes there were only two pieces ""in a similar posi' 

 tion," the larger one equal in length to the combined four pieces found in the smaller 

 specimen. In a third specimen studied by Hawkes a seventh branchial arch v,^s entirely 

 lacking. Oi two specimens examined by Goodey ' 1910.1\ in one this arch u-as lacking, 

 in the other it u-as represented (Text-figure 26a. vha. IT} by ""a pair of small, segmental 

 tapering pieces h"ing on the ventral side of the last basibranchial at the bases of the 

 sixth ceratobranchials."" In a specimen described and figured by Garman ' 1913i the 

 vestigial seventh arch >my Text-figure 26b > is represented by a pair of cartilages consider- 

 ably larger than any described or figured in other specimens. The seventh branchial 

 arch of a specimen studied by Allis is shown in my Figures 8 and 9, plate III, and is 

 described by AlHs 1923, p. 179'i as rollows: 



Fr;— :he !ef: -:;:er; litaril c:~er :: :r.e ;:>::-. -.?:branchial, a chain of small thin nodules 

 of ca":li;e exter.ij rcitencrly ini rerreser.:; :l-e . e;::gial seventh ceratobranchial . . . On 

 the r:;r.: ;i ie of the head this chain of nodules is represented by a process of the basibranchial. 

 Wedjed m between the base of this process and the distal end of the sixth ceratobranchial 



