226 



AYERS AND JACKSON. 



EXPLANATION OF PLATE XXIIL 



Fig. 7. A dorsal view of the skull of Bdellostoma, cranium, olfactory capsule 

 and nasal tube removed (X 2|). 



Fig. S. The basal plate of Bdellostoma, ventral view ( x i). 



Fig. 9. A dorsal view of the basal plate of Bdellostoma (x i). 



Fig. 10. Dorsal view of the teeth and the dental plate of Bdellostoma (x 2). 



The dental plate of Bdellostoma, ventral view ( X 2). 



A gill bar of Bdellostoma, stretched out (X 8). 



The cartilage of the oesophago-cutaneous duct of Bdellostoma ( x 4). 



The skeleton of the posterior region of Bdellostoma (x i). 



A cross-section of the tail of Bdellostoma, taken just in front of r, 



Fig. II 



Fig. 12 

 Fig. 13 

 Fig. 14 

 Fig. i t; 

 Fig. 14- 



Dorsal and ventral portion of section not shown ( x 10). 



A.i. 



— internal bars of anterior seg- 

 ment. 

 = external bars of anterior seg- 

 ment. 

 = lateral dental plate. 

 = cloacal cartilage. 

 = anterior transverse velar bar. 

 = blood vessel. 

 = palatine commissure. 

 = process of median ventral 



cartilage. 

 = connective tissue. 

 = dermal muscle layer. 

 = dorsal fin. 

 e. = posterior external process of 



lateral plate. 

 ex.g.p.-=^ external gill passage. 

 / = auditory foramen. 

 = fin-ray. 



= dorsal tendon groove. 

 = superior process of oesophago- 

 cutaneous cartilage. 



A.c. 



a.a. 

 a.v. 

 a.b. 

 b.v. 

 cm. 



en. 



D.m 



D.F. 



f.r. 



K. - 



M.D. = 



M.V. = 



Me. = 



M.d. = 



My. - 



oes. b. = 



p.b. = 



p.a. — 



S.I. = 



T.I. - 



tr. = 



V.F. = 



posterior internal process of 



lateral plate, 

 anterior process of hypophysial 



plate, 

 median dorsal bar. 

 median ventral bar. 

 median cartilage bar. 

 median piece of dental plate, 

 myotome. 



the oesophago-cutaneous bar. 

 posterior transverse velar bar. 

 posterior arch of dental plate, 

 anterior connecting process of 



lateral plate, 

 sheath of fin-ray. 

 epidermis. 



transverse labial cartilage, 

 anterior process of trabeculae. 

 ventral fin. 

 posterior connecting process 



of lateral plate. 



